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NCERT Solutions for Class 8 Maths Chapter 9 Algebraic Expressions and Identities

NCERT Solutions for Class 8 Maths Chapter 9 Algebraic Expressions and Identities

Edited By Ramraj Saini | Updated on Mar 01, 2024 06:31 PM IST

Algebraic Expressions and Identities Class 8 Questions And Answers provided here. These NCERT Solutions are prepared by experts team at Careers360 team considering the latest syllabus and pattern of CBSE 2023-24. This chapter will introduce you to the application of algebraic terms and variables to solve various problems. Algebra is the most important branch of mathematics which teaches how to form equations and solving them using different kinds of techniques. Important topics like the product of the equation, finding the coefficient of the variable in the equation, subtraction of the equation and creating quadratic equation by the product of its two roots, and division of the equation are covered in this chapter. Also Practice NCERT solutions for class 8 maths to command the concepts.

This Story also Contains
  1. Algebraic Expressions and Identities Class 8 Questions And Answers PDF Free Download
  2. Algebraic Expressions and Identities Class 8 Solutions - Important Formulae
  3. Algebraic Expressions and Identities Class 8 NCERT Solutions (Intext Questions and Exercise)
  4. NCERT Solutions for Class 8 Maths Chapter 9 Algebraic Expressions and Identities - Topics
  5. NCERT Solutions for Class 8 Maths - Chapter Wise
  6. NCERT Solutions for Class 8 - Subject Wise
  7. Also Check NCERT Books and NCERT Syllabus here
NCERT Solutions for Class 8 Maths Chapter 9 Algebraic Expressions and Identities
NCERT Solutions for Class 8 Maths Chapter 9 Algebraic Expressions and Identities

Algebraic Expressions and Identities Class 8 Questions And Answers PDF Free Download

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Algebraic Expressions and Identities Class 8 Solutions - Important Formulae

  • (a + b)2 = a2 + 2ab + b2

  • (a - b)2 = a2 - 2ab + b2

  • (a + b)(a - b) = a2 - b2

  • (x + a)(x + b) = x2 + (a + b)x + ab

  • (x + a)(x - b) = x2 + (a - b)x - ab

  • (x - a)(x + b) = x2 + (b - a)x - ab

  • (x - a)(x - b) = x2 - (a + b)x + ab

  • (a + b)3 = a3 + b3 + 3ab(a + b)

  • (a - b)3 = a3 - b3 - 3ab(a - b)

Free download NCERT Solutions for Class 8 Maths Chapter 9 Algebraic Expressions and Identities for CBSE Exam.

Algebraic Expressions and Identities Class 8 NCERT Solutions (Intext Questions and Exercise)

NCERT Solutions to Exercises of Chapter 9: Algebraic Expressions and Identities

what are expressions?

Question: 1 Give five examples of expressions containing one variable and five examples of expressions containing two variables.

Answer:

Five examples of expressions containing one variable are:

x4,y,3z,p2,2q3

Five examples of expressions containing two variables are:

x+y,3p4q,ab,uv2,z2+x3

Question: 2(i) Show on the number line

x

Answer:

x on the number line:

1643105164197

Question: 2(ii) Show on the number line :

x4

Answer:

x-4 on the number line:

1643105231337

Question: 2(iii) Show on the number line :

2x+1

Answer:

2x+1 on the number line:

c360_4-1


Question: 2(iv) Show on the number line:

3x2

Answer:

3x - 2 on the number line

1643105272368

Algebraic expressions and identities class 8 solutions - Topic 9.2 Terms, Factors and Coefficients

Question:1 Identify the coefficient of each term in the expression.

x2y210x2y+5xy220

Answer:

coefficient of each term are given below

The coefficient of x2y2 is\1The coefficient of x2y is 10The coefficient of xy2 is\5

Algebraic expressions and identities class 8 ncert solutions - Topic 9.3 Monomials, Binomials and Polynomials

Question: 1(i) Classify the following polynomials as monomials, binomials, trinomials.

z+5

Answer:

Binomial since there are two terms with non zero coefficients.

Question: 1(ii) Classify the following polynomials as monomials, binomials, trinomials.

x+y+z

Answer:

Trinomial since there are three terms with non zero coefficients.

Question:1(iii) Classify the following polynomials as monomials, binomials, trinomials.

y+z+100

Answer:

Trinomial since there are three terms with non zero coefficients.

Question: 1(iv) Classify the following polynomials as monomials, binomials, trinomials.

abac

Answer:

Binomial since there are two terms with non zero coefficients.

Question: 1(v) Classify the following polynomials as monomials, binomials, trinomials.

17

Answer:

Monomial since there is only one term.

Question: 2(a) Construct 3 binomials with only x as a variable;

Answer:

Three binomials with the only x as a variable are:

x+2, x+x2, 3x35x4

Question: 2(b) Construct 3 binomials with x and y as variables;

Answer:

Three binomials with x and y as variables are:

x+y, x7y,xy2+2xy

Question: 2(c) Construct 3 monomials with x and y as variables;

Answer:

Three monomials with x and y as variables are

xy, 3xy4, 2x3y2

Question: 2(d) Construct 2 polynomials with 4 or more terms .

Answer:

Two polynomials with 4 or more terms are:

a+b+c+d,x3xy+2y+4xy2

NCERT Solutions for Class 8 Maths Chapter 9 Algebraic Expressions and Identities Topic 9.4 Like and Unlike Terms

Question:(i) Write two terms which are like

7xy

Answer:

Two terms like 7xy are:3xy and 5xy

Question:(ii) Write two terms which are like

4mn2

Answer:

Two terms which are like 4mn2 are:mn2 and3mn2.

we can write more like terms

Question:(iii) Write two terms which are like

2l

Answer:

Two terms which are like 2l are:l and 3l

NCERT Solutions for Class 8 Maths Chapter 9 Algebraic Expressions and Identities - Exercise: 9.1

Question:1(i) Identify the terms, their coefficients for each of the following expressions.

5xyz23zy

Answer

following are the terms and coefficient

The terms are 5xyz2 and 3zy and the coefficients are 5 and -3.

Question: 1(ii) Identify the terms, their coefficients for each of the following expressions.

1+x+x2

Answer:

the following is the solution

The terms are 1, x, and x2 and the coefficients are 1, 1, and 1 respectively.

Question:1(iii) Identify the terms, their coefficients for each of the following expressions.

4x2y24x2y2z2+z2

Answer:

The terms are 4x2y2, 4x2y2z2and z2 and the coefficients are 4, 4 and 1 respectively.

Question: 1(iv) Identify the terms, their coefficients for each of the following expressions.

3pq+qrrp

Answer:

The terms are 3, -pq, qr,and -rp and the coefficients are 3, -1, 1 and -1 respectively.

Question:1(v) Identify the terms, their coefficients for each of the following expressions.

x2+y2xy

Answer:

The terms are x2, y2 and xy and the coefficients are 12, 12 and 1 respectively.

Above are the terms and coefficients

Question: 1(vi) Identify the terms, their coefficients for each of the following expressions.

0.3a0.6ab+0.5b

Answer:

The terms are 0.3a, -0.6ab and 0.5b and the coefficients are 0.3, -0.6 and 0.5.

Question: 2(c) Classify the following polynomials as monomials, binomials, trinomials. Which polynomials do not fit in any of these three categories?

x+x2+x3+x4

Answer:

This polynomial does not fit in any of these three categories.

Question: 2(i) Classify the following polynomials as monomials, binomials, trinomials. Which polynomials do not fit in any of these three categories?

ab+bc+cd+da

Answer:

This polynomial does not fit in any of these three categories.

Question: 3(i) Add the following.

abbc,bcca,caab

Answer:

ab-bc+bc-ca+ca-ab=0.

Question:3 (ii) Add the following.

ab+ab,bc+bc,ca+ac

Answer:

ab+ab+bc+bc+ca+ac=(aa)+(bb)+(cc)+ab+bc+ac=ab+bc+ca

Question:3 (iii) Add the following

2p2q23pq+4,5+7pq3p2q2

Answer:

2p2q23pq+4+5+7pq3p2q2=(23)p2q2+(3+7)pq+4+5=p2q2+4pq+9

Question: 3(iv) Add the following.

l2+m2+n2,n2+l2,2lm+2mn+2nl

Answer:

l2+m2+n2+n2+l2+2lm+2mn+2nl=2l2+m2+2n2+2lm+2mn+2nl

Question: 4(a) Subtract 4a7ab+3b+12 from 12a9ab+5b3

Answer:

12a-9ab+5b-3-(4a-7ab+3b+12)
=(12-4)a +(-9+7)ab+(5-3)b +(-3-12)
=8a-2ab+2b-15

Question: 4(b) Subtract 3xy+5yz7zx from 5xy2yz2zx+10xyz

Answer:

5xy2yz2zx+10xyz(3xy+5yz7zx)=(53)xy+(25)yz+(2+7)zx+10xyz=2xy7yz+5zx+10xyz

Question: 4(c) Subtract 4p2q3pq+5pq28p+7q10 from 183p11q+5pq2pq2+5p2q

Answer:

183p11q+5pq2pq2+5p2q(4p2q3pq+5pq28p+7q10)=18(10)3p(8p)11q7q+5pq(3pq)2pq25pq2+5p2q4p2q=28+5p18q+8pq7pq2+p2q

NCERT class 8 maths chapter 9 question answer - Topic 9.7.2 Multiplying Three or More Monomials

Question:1 Find 4x×5y×7z . First find 4x×5y and multiply it by 7z ; or first find 5y×7z and multiply it by 4x .

Answer:

4x×5y×7z=(4x×5y)×7z=20xy×7z=140xyz4x×5y×7z=(5y×7z)×4x=35yz×4x=140xyz

We observe that the result is same in both cases and the result does not depend on the order in which multiplication has been carried out.

Class 8 maths chapter 9 question answer - exercise: 9.2

Question: 1(i) Find the product of the following pairs of monomials.

4,7p

Answer:

4×7p=28p

Question: 1(ii) Find the product of the following pairs of monomials.

4p,7p

Answer:

4p×7p=(4×7)p×p=28p2

Question: 1(iii) Find the product of the following pairs of monomials

4p,7pq

Answer:

4p×7pq=(4×7)p×pq=28p2q

Question: 1(iv) Find the product of the following pairs of monomials.

4p3,3p

Answer:

4p3×(3p)=4×(3)p3×p=12p4

Question:2(A) Find the areas of rectangles with the following pairs of monomials as their lengths and breadths respectively.

(p,q)

Answer:

The question can be solved as follows

Area=length×breadth=(p×q)=pq

Question:2(B) Find the areas of rectangles with the following pairs of monomials as their lengths and breadth respectively.

(10m,5n)

Answer:

the area is calculated as follows

Area=length×breadth=10m×5n=50mn

Question:2(C) Find the areas of rectangles with the following pairs of monomials as their lengths and breadths respectively.

(20x2,5y2)

Answer:

the following is the solution

Area=length×breadth=20x2×5y2=100x2y2

Question:2(D) Find the areas of rectangles with the following pairs of monomials as their lengths and breadths respectively.

(4x,3x2)

Answer:

area of rectangles is

Area=length×breadth=4x×3x2=12x3

Question:2(E) Find the areas of rectangles with the following pairs of monomials as their lengths and breadths respectively.

(3mn,4np)

Answer:

The area is calculated as follows

Area=length×breadth=3mn×4np=12mn2p

Question:3 Complete the table of products.


First monomial

Second monomial

2x

5y

3x2

4xy

7x2y

9x2y2

2x

4x2


...

...

...

...

...

5y

...

...

15x2y

...

...

...

3x2

...

...

...

...

...

...

4xy

...

...

...

...

...

...

7x2y

...

...

...

...

...

...

9x2y2

...

...

...

...

...

...

Answer:

First monomial

Second monomial

2x

5y

3x2

4xy

7x2y

9x2y2

2x

4x2

10xy

6x3

8x2y

14x3y

18x3y2

5y

10xy

25y2

15x2y

20xy2

35x2y2

45x2y3

3x2

6x3

15x2y

9x4

12x3y

21x4y

27x4y2

4xy

8x2y

20xy2

12x3y

16x2y2

28x3y

36x3y3

7x2y

14x3y

35x2y2

21x4y

28x3y2

49x4y2

63x4y3

9x2y2

18x3y2

45x2y3

27x4y2

36x3y3

63x4y3

81x4y4

Question:4(i) Obtain the volume of rectangular boxes with the following length, breadth and height respectively.

5a,3a2,7a4

Answer:

Volume=length×breadth×height=5a×3a2×7a4=15a3×7a4=105a7

Question:4(ii) Obtain the volume of rectangular boxes with the following length, breadth and height respectively.

2p,4q,8r

Answer:

the volume of rectangular boxes with the following length, breadth and height is

Volume=length×breadth×height=2p×4q×8r=8pq×8r=64pqr

Question:4(iii) Obtain the volume of rectangular boxes with the following length, breadth and height respectively.

xy,2x2y,2xy2

Answer:

the volume of rectangular boxes with the following length, breadth and height is

Volume=length×breadth×height=xy×2x2y×2xy2=2x3y2×2xy2=4x4y4

Question:4(iv) Obtain the volume of rectangular boxes with the following length, breadth and height respectively.

a,2b,3c

Answer:

the volume of rectangular boxes with the following length, breadth and height is

Volume=length×breadth×height=a×2b×3c=2ab×3c=6abc

Question:5(i) Obtain the product of

xy,yz,zx

Answer:

the product

xy×yz×zx=xy2z×zx=x2y2z2

Question:5(ii) Obtain the product of

a,a2,a3

Answer:

the product

a×(a2)×a3=a3×a3=a6

Question:5(iii) Obtain the product of

2, 4y, 8y2, 16y3

Answer:

the product

2×4y×8y2×16y3=8y×8y2×16y3=64y3×16y3=1024y6

Question:5(iv) Obtain the product of

a,2b,3c,6abc

Answer:

the product

a×2b×3c×6abc=2ab×3c×6abc=6abc×6abc=36a2b2c2

Question:5(v) Obtain the product of

m,mn,mnp

Answer:

the product

m×(mn)×mnp=m2n×mnp=m3n2p

Class 8 maths chapter 9 NCERT solutions - Topic 9.8.1 Multiplying a Monomial by a Binomial

Question:(i) Find the product

2x(3x+5xy)

Answer:

Using distributive law,

2x(3x+5xy)=6x2+10x2y

Question:(ii) Find the product

a2(2ab5c)

Answer:

Using distributive law,

We have : a2(2ab5c)=2a3b5a2c

NCERT Solutions for Class 8 Maths Chapter 9 Algebraic Expressions and Identities - Topic 9.8.2 Multiplying A Monomial By A Trinomial

Question:1 Find the product:

(4p2+5p+7)×3p

Answer:

By using distributive law,

(4p2+5p+7)×3p=12p3+15p2+21p

Class 8 maths chapter 9 NCERT solutions - exercise: 9.3

Question:1(i) Carry out the multiplication of the expressions in each of the following pairs.

4p,q+r

Answer:

Multiplication of the given expression gives :

By distributive law,

(4p)(q+r)=4pq+4pr

Question:1(ii) Carry out the multiplication of the expressions in each of the following pairs.

ab,ab

Answer:

We have ab, (a-b).

Using distributive law we get,

ab(ab)=a2bab2

Question:1(iii) Carry out the multiplication of the expressions in each of the following pairs.

a+b,7a2b2

Answer:

Using distributive law we can obtain multiplication of given expression:

(a+b)(7a2b2)=7a3b2+7a2b3

Question:1(iv) Carry out the multiplication of the expressions in each of the following pairs.

a29,4a

Answer:

We will obtain multiplication of given expression by using distributive law :

(a29)(4a)=4a336a

Question:1(v) Carry out the multiplication of the expressions in each of the following pairs.

pq+qr+rp,0

Answer:

Using distributive law :

(pq+qr+rp)(0)=pq(0)+qr(0)+rp(0)=0

Question:2 Complete the table


First expression

Second expression

Product

(i)

a

b+c+d

...

(ii)

x+y5

5xy

...

(iii)

p

6p27p+5

...

(iv)

4p2q2

p2q2

...

(v)

a+b+c

abc

...


Answer:

We will use distributive law to find product in each case.


First expression

Second expression

Product

(i)

a

b+c+d

ab+ac+ad

(ii)

x+y5

5xy

5x2y+5xy225xy

(iii)

p

6p27p+5

6p37p2+5p

(iv)

4p2q2

p2q2

4p4q24p2q4

(v)

a+b+c

abc

a2bc+ab2c+abc2


Question:3(i) Find the product.

(a2)×(2a22)×(4a26)


Answer:

Opening brackets :

(a2)×(2a22)×(4a26)=(a2×2a22)×(4a26)=2a24×4a26

or =8a50

Question:3(ii) Find the product.

(23xy)×(910x2y2)

Answer:

We have,

(23xy)×(910x2y2)=35x3y3

Question:3(iii) Find the product.

(103pq3)×(65p3q)

Answer:

We have

(103pq3)×(65p3q)=4p4q4

Question:3(iv) Find the product.

x×x2×x3×x4

Answer:

We have x×x2×x3×x4

x×x2×x3×x4=(x×x2)×x3×x4

or (x3)×x3×x4

=x10

Question:4(a) Simplify 3x(4x5)+3 and find its values for

(i) x=3

Answer:

(a) We have

3x(4x5)+3=12x215x+3

Put x = 3,

We get : 12(3)215(3)+3=12(9)45+3=10842=66


Question:4(a) Simplify 3x(4x5)+3 and find its values for

(ii) x=12

Answer:

We have

3x(4x5)+3=12x215x+3

Put

x=12

. So We get,

12x215x+3=12(12)215(12)+3=6152=32

Question:4(b) Simplify a(a2+a+1)+5 and find its value for

(i) a=0

Answer:

We have : a(a2+a+1)+5=a3+a2+a+5

Put a = 0 : =03+02+0+5=5

Question:4(b) Simplify a(a2+a+1)+5 and find its value for

(ii) a=1

Answer:

We have a(a2+a+1)+5=a3+a2+a+5

Put a = 1 ,

we get : 13+12+1+5=1+1+1+5=8

Question:4(b) Simplify a(a2+a+1)+5 and find its value for

(iii) a=1

Answer:

We have a(a2+a+1)+5 .

or a(a2+a+1)+5=a3+a2+a+5

Put a = (-1)

=(1)3+(1)2+(1)+5=1+11+5=4

Question:5(a) Add: p(pq),q(qr) and r(rp)

Answer:

(a)First we will solve each brackets individually.

p(pq)=p2pq ; q(qr)=q2qr ; r(rp)=r2rp

Addind all we get : p2pq+q2qr+r2rp

=p2+q2+r2pqqrrp

Question:5(b) Add: 2x(zxy) and 2y(zyx)

Answer:

Firstly, open the brackets:

2x(zxy)=2xz2x22xy

and 2y(zyx)=2yz2y22xy

Adding both, we get :

2xz2x22xy+2yz2y22xy

or =2x22y24xy+2xz+2yz

Question:5(c) Subtract: 3l(l4m+5n) from 4l(10n3m+2l)

Answer:

At first we will solve each bracket individually,

3l(l4m+5n)=3l212lm+15ln

and 4l(10n3m+2l)=40ln12ml+8l2

Subtracting:

40ln12ml+8l2(3l212lm+15ln)

or =40ln12ml+8l23l2+12lm15ln

or =25ln+5l2

Question:5(d) Subtract: 3a(a+b+c)2b(ab+c) from 4c(a+b+c)

Answer:

Solving brackets :

3a(a+b+c)2b(ab+c)=3a2+3ab+3ac2ab+2b22bc

=3a2+ab+3ac+2b22bc

and 4c(a+b+c)=4ac+4bc+4c2

Subtracting : 4ac+4bc+4c2(3a2+ab+3ac+2b22bc)

=4ac+4bc+4c23a2ab3ac2b2+2bc

=3a22b2+4c2ab+6bc7ac

NCERT Solutions for Class 8 Maths Chapter 9 Algebraic Expressions And Identities-Exercise: 9.4

Question:1(i) Multiply the binomials.

(2x+5) and (4x3)

Answer:

We have (2x + 5) and (4x - 3)
(2x + 5) X (4x - 3) = (2x)(4x) + (2x)(-3) + (5)(4x) + (5)(-3)
= 8 x2 - 6x + 20x - 15
= 8 x2 + 14x -15

Question:1(ii) Multiply the binomials.

(y8) and (3y4)

Answer:

We need to multiply (y - 8) and (3y - 4)
(y - 8) X (3y - 4) = (y)(3y) + (y)(-4) + (-8)(3y) + (-8)(-4)
= 3 y2 - 4y - 24y + 32
= 3 y2 - 28y + 32

Question:1(iii) Multiply the binomials

(2.5l0.5m) and (2.5l+0.5m)

Answer:

We need to multiply (2.5l - 0.5m) and (2.5l + 0..5m)
(2.5l - 0.5m) X (2.5l + 0..5m) = (2.5l)2(0.5m)2 using (ab)(a+b)=(a)2(b)2
= 6.25 l2 - 0.25 m2

Question:1(iv) Multiply the binomials.

(a+3b) and (x+5)

Answer:

(a + 3b) X (x + 5) = (a)(x) + (a)(5) + (3b)(x) + (3b)(5)
= ax + 5a + 3bx + 15b

Question:1(v) Multiply the binomials.

(2pq+3q2) and (3pq2q2)

Answer:

(2pq + 3q 2 ) X (3pq - 2q 2 ) = (2pq)(3pq) + (2pq)(-2q 2 ) + ( 3q 2 )(3pq) + (3q 2 )(-2q 2 )
= 6p 2 q 2 - 4pq 3 + 9pq 3 - 6q 4
= 6p 2 q 2 +5pq 3 - 6q 4

Question:1(vi) Multiply the binomials.

(34a2+3b2) and 4(a223b2)

Answer:

Multiplication can be done as follows

(34a2+3b2) X (4a283b2) = 3a24×4a2+3a24×(8b23)+3b2×4a2+3b2×(8b23)


= 3a42a2b2+12a2b28b4

= 3a4+10a2b28b4

Question:2(i) Find the product.

(52x) (3+x)

Answer:

(5 - 2x) X (3 + x) = (5)(3) + (5)(x) +(-2x)(3) + (-2x)(x)
= 15 + 5x - 6x - 2 x2
= 15 - x - 2 x2

Question:2(ii) Find the product.

(x+7y)(7xy)

Answer:

(x + 7y) X (7x - y) = (x)(7x) + (x)(-y) + (7y)(7x) + (7y)(-y)
= 7 x2 - xy + 49xy - 7 y2
= 7 x2 + 48xy - 7 y2

Question:2(iii) Find the product.

(a2+b)(a+b2)

Answer:

( a2 + b) X (a + b2 ) = ( a2 )(a) + ( a2 )( b2 ) + (b)(a) + (b)( b2 )
= a3+a2b2+ab+b3

Question:2(iv) Find the product.

(p2q2)(2p+q)

Answer:

following is the solution

( p2q2 ) X (2p + q) = (p2)(2p)+(p2)(q)+(q2)(2p)+(q2)(q)
2p3+p2q2q2pq3

Question:3(i) Simplify.

(x25)(x+5)+25

Answer:

this can be simplified as follows

( x2 -5) X (x + 5) + 25 = ( x2 )(x) + ( x2 )(5) + (-5)(x) + (-5)(5) + 25
= x3+5x25x25+25
= x3+5x25x

Question:3(ii) Simplify .

(a2+5)(b3+3)+5

Answer:

This can be simplified as

( a2 + 5) X ( b3 + 3) + 5 = ( a2 )( b3 ) + ( a2 )(3) + (5)( b3 ) + (5)(3) + 5
= a2b3+3a2+5b3+15+5
= a2b3+3a2+5b3+20

Question:3(iii) Simplify.

(t+s2)(t2s)

Answer:

simplifications can be

(t + s2 )( t2 - s) = (t)( t2 ) + (t)(-s) + ( s2 )( t2 ) + ( s2 )(-s)
= t3ts+s2t2s3

Question:3(iv) Simplify.

(a+b)(cd)+(ab)(c+d)+2(ac+bd)

Answer:

(a + b) X ( c -d) + (a - b) X (c + d) + 2(ac + bd )
= (a)(c) + (a)(-d) + (b)(c) + (b)(-d) + (a)(c) + (a)(d) + (-b)(c) + (-b)(d) + 2(ac + bd )
= ac - ad + bc - bd + ac +ad -bc - bd + 2(ac + bd )
= 2(ac - bd ) + 2(ac +bd )
= 2ac - 2bd + 2ac + 2bd
= 4ac

Question:3(v) Simplify.

(x+y)(2x+y)+(x+2y)(xy)

Answer:

(x + y) X ( 2x + y) + (x + 2y) X (x - y)
=(x)(2x) + (x)(y) + (y)(2x) + (y)(y) + (x)(x) + (x)(-y) + (2y)(x) + (2y)(-y)
= 2 x2 + xy + 2xy + y2 + x2 - xy + 2xy - 2 y2
=3 x2 + 4xy - y2

Question:3(vi) Simplify.

(x+y)(x2xy+y2)

Answer:

simplification is done as follows

(x + y) X ( x2xy+y2 ) = x X ( x2xy+y2 ) + y ( x2xy+y2 )
= x3x2y+xy2+yx2xy2+y3
= x3+y3

Question:3(vii) Simplify.

(1.5x4y)(1.5x+4y+3)4.5x+12y

Answer:

(1.5x - 4y) X (1.5x + 4y + 3) - 4.5x + 12y = (1.5x) X (1.5x + 4y + 3) -4y X (1.5x + 4y + 3) - 4.5x + 12y
= 2.25 x2 + 6xy + 4.5x - 6xy - 16 y2 - 12y -4.5x + 12 y
= 2.25 x2 - 16 y2

Question:3(viii) Simplify.

(a+b+c)(a+bc)

Answer:

(a + b + c) X (a + b - c) = a X (a + b - c) + b X (a + b - c) + c X (a + b - c)
= a2 + ab - ac + ab + b2 -bc + ac + bc - c2
= a2 + b2 - c2 + 2ab

NCERT Solutions for Class 8 Maths Chapter 9 Algebraic Expressions And Identities - Topic 9.11 Standard Identities

Question:1(i) Put -b in place of b in identity 1. Do you get identity 2?

Answer:

Identity 1 (a+b)2=a2+2ab+b2
If we replace b with -b in identity 1
We get,
a2+2a(b)+(b)2=a22ab+b2
which is equal to
(ab)2 which is identity 2
So, we get identity 2 by replacing b with -b in identity 1

NCERT Free Solutions for Class 8 Maths Chapter 9 Algebraic Expressions And Identities - Topic 9.11 Standard Identities

Question:1 Verify Identity (IV), for a=2,b=3,x=5 .

Answer:

Identity IV
(a + x)(b + x) = x2+(a+b)x+ab
So, it is given that a = 2, b = 3 and x = 5
Lets put these value in identity IV
(2 + 5)(3 + 5) = 52 + (2 + 3)5 +2 X 3
7 X 8 = 25 + 5 X 5 + 6
56 = 25 + 25 + 6
= 56
L.H.S. = R.H.S.
So, by this we can say that identity IV satisfy with given value of a,b and x

Question:2 Consider, the special case of Identity (IV) with a = b, what do you get? Is it related to Identity

Answer:

Identity IV is (a+x)(b+x)=x2+(a+b)x+ab
If a =b than

(a + x)(a + x) = x2+(a+a)x+a×a
(a+x)2=x2+2ax+a2
Which is identity I

Question:3 Consider, the special case of Identity (IV) with a=c and b=c What do you get? Is it related to Identity ?

Answer:

Identity IV is (a+x)(b+x)=x2+(a+b)x+ab
If a = b = -c than,
(x - c)(x - c) = x2+(c+(c))x+(c)×(c)
(xc)2=x2+2cx+c2
Which is identity II

Question:4 Consider the special case of Identity (IV) with b=a . What do you get? Is it related to Identity?

Answer:

Identity IV is (a+x)(b+x)=x2+(a+b)x+ab
If b = -a than,

(x + a)(x - a) = x2+(a+(a))x+(a)×a
= x2a2
Which is identity III

Class 8 algebraic expressions and identities NCERT solutions - exercise: 9.5

Question:1(i) Use a suitable identity to get each of the following products.

(x+3)(x+3)

Answer:

(x + 3) X (x +3) = (x+3)2
So, we use identity I for this which is
(a+b)2=a2+2ab+b2
In this a=x and b = x
(x+3)2=x2+2(x)(3)+32
= x2+6x+9

Question:1(ii) Use a suitable identity to get each of the following products in bracket.

(2y+5)(2y+5)

Answer:

(2y + 5) X ( 2y + 5) = (2y+5)2
We use identity I for this which is
(a+b)2=a2+2ab+b2
IN this a = 2y and b = 5
(2y+5)2=(2y)2+2(2y)(5)+52
= (2y+5)2=4y2+20y+25

Question:1(iii) Use a suitable identity to get each of the following products in bracket.

(2a7)(2a7)

Answer:

(2a -7) X (2a - 7) = (2a7)2
We use identity II for this which is
(ab)2=a22ab+b2
in this a = 2a and b = 7
(2a7)2=(2a)22(2a)(7)+72
= 4a228a+49

Question:1(iv) Use a suitable identity to get each of the following products in bracket.

(3a12)(3a12)

Answer:

(3a12)×(3a12)=((3a12))2
We use identity II for this which is
(ab)2=a22ab+b2
in this a = 3a and b = -1/2
(3a12)2=(3a)22(3a)(12)+(12)2
= 9a23a+14

Question:1(v) Use a suitable identity to get each of the following products in bracket.

(1.1m4)(1.1m+4)

Answer:

(1.1m4)(1.1m+4)
We use identity III for this which is
(a - b)(a + b) = a2b2
In this a = 1.1m and b = 4
(1.1m4)(1.1m+4) = (1.1m)2(4)2
= 1.21 m2 - 16

Question:1(vi) Use a suitable identity to get each of the following products in bracket.

(a2+b2)(a2+b2)

Answer:

take the (-)ve sign common so our question becomes
- (a2+b2)(a2b2)
We use identity III for this which is
(a - b)(a + b) = a2b2
In this a = a2 and b = b2

(a2+b2)(a2b2) = ((a2)2(b2)2)=a4+b4

Question:1(vii) Use a suitable identity to get each of the following.

(6x7)(6x+7)

Answer:

(6x -7) X (6x - 7) = (6x7)2
We use identity III for this which is
(a - b)(a + b) = a2b2
In this a = 6x and b = 7
(6x -7) X (6x - 7) = (6x)2(7)2=36x249

Question:1(viii) Use a suitable identity to get each of the following product.

(a+c)(a+c)

Answer:

take (-)ve sign common from both the brackets So, our question become
(a -c) X (a -c) = (ac)2
We use identity II for this which is
(ab)2=a22ab+b2
In this a = a and b = c
(ac)2=a22ac+c2

Question:1(ix) Use a suitable identity to get each of the following product.

(x2+3y4)(x2+3y4)

Answer:

(x2+3y4)×(x2+3y4)=(x2+3y4)2

We use identity I for this which is
(a+b)2=a2+2ab+b2
In this a = x2 and b = 3y4

(x2+3y4)2=(x2)2+2(x2)(3y4)+(3y4)2
= x24+3xy4+9y216

Question:1(x) Use a suitable identity to get each of the following products.

(7a9b)(7a9b)

Answer:

(7a9b)×(7a9b)=(7a9b)2


We use identity II for this which is
(ab)2=a22ab+b2
In this a = 7a and b = 9b
(7a9b)2=(7a)22(7a)(9b)+(9b)2
= 49a2126ab+81b2

Question:2(i) Use the identity (x+a)(x+b)=x2+(a+b)x+ab to find the following products.

(x+3)(x+7)

Answer:

We use identity (x+a)(x+b)=x2+(a+b)x+ab
in this a = 3 and b = 7
(x+3)(x+7) = x2+(3+7)x+3×7
= x2+10x+21

Question:2(ii) Use the identity (x+a)(x+b)=x2+(a+b)x+ab to find the following products.

(4x+5)(4x+1)

Answer:

We use identity (x+a)(x+b)=x2+(a+b)x+ab
In this a= 5 , b = 1 and x = 4x
(4x+5)(4x+1) = (4x)2+(5+1)4x+(5)(1)
= 16x2+24x+5

Question:2(iii) Use the identity (x+a)(x+b)=x2+(a+b)x+ab to find the following products.

(4x5)(4x1)

Answer:

We use identity (x+a)(x+b)=x2+(a+b)x+ab
in this x = 4x , a = -5 and b = -1
(4x5)(4x1) = (4x)2+(51)4x+(5)(1)
= 16x224x+5

Question:1(iv) Use the identity (x+a)(x+b)=x2+(a+b)x+ab to find the following products.

(4x+5)(4x1)

Answer:

We use identity (x+a)(x+b)=x2+(a+b)x+ab
In this a = 5 , b = -1 and x = 4x
(4x+5)(4x1) = (4x)2+(5+(1))4x+(5)(1)
= 16x2+16x5

Question:2(v) Use the identity (x+a)(x+b)=x2+(a+b)x+ab to find the following products.

(2x+5y)(2x+3y)

Answer:

We use identity (x+a)(x+b)=x2+(a+b)x+ab
In this a = 5y , b = 3y and x = 2x
(2x+5y)(2x+3y) = (2x)2+(5y+3y)(2x)+(5y)(3y)
= 4x2+16xy+15y2

Question:2(vi) Use the identity (x+a)(x+b)=x2+(a+b)x+ab to find the following products.

(2a2+9)(2a2+5)

Answer:

We use identity (x+a)(x+b)=x2+(a+b)x+ab
In this a = 9 , b = 5 and x = 2a2
(2a2+9)(2a2+5) = (2a2)2+(9+5)2a2+(9)(5)
= 4a4+28a2+45

Question:2(vii) Use the identity (x+a)(x+b)=x2+(a+b)x+ab to find the following products.

(xyz4)(xyz2)

Answer:

We use identity (x+a)(x+b)=x2+(a+b)x+ab
In this a = -4 , b = -2 and x = xyz
(xyz4)(xyz2) = (xyz)2+((4)+(2))xyz+(4)(2)
= x2y2z26xyz+8

Question:3(i) Find the following squares by using the identities.

(b7)2

Answer:

We use identity
(ab)2=a22ab+b2
In this a =b and b = 7
(b7)2=b22(b)(7)+72
= b214b+49

Question:3(ii) Find the following squares by using the identities.

(xy+3z)2

Answer:

We use
(a+b)2=a2+2ab+b2

In this a = xy and b = 3z
(xy+3z)2=(xy)2+2(xy)(3z)+(3z)2
= x2y2+6xyz+9z2

Question:3(iii) Find the following squares by using the identities.

(6x25y)2

Answer:

We use
(ab)2=a22ab+b2
In this a = 6x2 and b = 5y2
(6x5y)2=(6x)22(6x)(5y)+(5y)2
= 36x260xy+25y2

Question:3(iv) Find the following squares by using the identities.

(23m+32n)2

Answer:

we use the identity
(a+b)2=a2+2ab+b2
In this a = 2m3 and b = 3n2
(2m3+3n2)2=(2m3)2+2(2m3)(3n2)+(3n2)2

= 4m29+2mn+9n24

Question:3(v) Find the following squares by using the identities.

(0.4p0.5q)2

Answer:

we use
(ab)2=a22ab+b2
In this a = 0.4p and b =0.5q
(0.4p0.5q)2=(0.4p)22(0.4p)(0.5q)+(0.5q)2
= 0.16p20.4pq+0.25q2

Question:3(vi) Find the following squares by using the identities.

(2xy+5y)2

Answer:

we use the identity
(a+b)2=a2+2ab+b2
In this a = 2xy and b =5y
(2xy+5y)2=(2xy)2+2(2xy)(5y)+(5y)2
= 4x2y2+20xy2+25y2

Question:4(i) Simplify:

(a2b2)2

Answer:

we use
(ab)2=a22ab+b2
In this a = a2 and b = b2
(a2b2)2=(a2)22(a2)(b2)+(b2)2
= a42a2b2+b4

Question:4(ii) Simplify.

(2x+5)2(2x5)2

Answer:

we use
a2b2=(ab)(a+b)
In this a = (2x + 5) and b = (2x - 5)
(2x+5)2(2x5)2=((2x+5)(2x5))((2x+5)+(2x5))
= (2x+52x+5)(2x+5+2x5)
= (4x)(10)
=40x

or

remember that

(a+b)2(ab)2=4ab

here a= 2x, b= 5

4ab=4×2x×5=40x

Question:4(iii) Simplify.

(7m8n)2+(7m+8n)2

Answer:

we use
(ab)2=a22ab+b2 and (a+b)2=a2+2ab+b2
In this a = 7m and b = 8n
(7m8n)2=(7m)22(7m)(8n)+(8n)2
= 49m2112mn+64n2
and
(7m+8n)2=(7m)2+2(7m)(8n)+(8n)2
= 49m2+112mn+64n2

So, (7m8n)2+(7m+8n)2 = 49m2112mn+64n2 + 49m2+112mn+64n2
= 2(49m2+64n2)

or

remember that

(ab)2+(a+b)2=2(a2+b2)

Question: 4(iv) Simplify.

(4m+5n)2+(5m+4n)2

Answer:

we use
(a+b)2=a2+2ab+b2
1 ) In this a = 4m and b = 5n

(4m+5n)2=(4m)2+2(4m)(5n)+(5n)2
= 16m2+40mn+25n2
2 ) in this a = 5m and b = 4n
(5m+4n)2=(5m)2+2(5m)(4n)+(4n)2
= 25m2+40mn+16n2

So, (4m+5n)2+(5m+4n)2 = 16m2+40mn+25n2 + 25m2+40mn+16n2
= 41m2+80mn+41n2

Question: 4(v) Simplify.

(2.5p1.5q)2(1.5p2.5q)2

Answer:

we use
a2b2=(ab)(a+b)
1 ) In this a = (2.5p- 1.5q) and b = (1.5p - 2.5q)
(2.5p1.5q)2(1.5p2.5q)2=((2.5p1.5q)(1.5p2.5q))((2.5p1.5q)+(1.5p2.5q))
= (2.5p1.5q1.5p+2.5q)(2.5p1.5q+1.5p2.5q)
= 4(p + q ) (p - q)
= 4 (p2q2)

Question:4(vi) Simplify.

(ab+bc)22ab2c

Answer:

We use identity
(a+b)2=a2+2ab+b2
In this a = ab and b = bc
(ab+bc)2=(ab)2+2(ab)(bc)+(bc)2
= a2b2+2ab2c+b2c2
Now, a2b2+2ab2c+b2c2 - 2ab2c
= a2b2+b2c2

Question:4(vii) Simplify.

(m2n2m)2+2m3n2

Answer:

We use identity
(ab)2=a22ab+b2
In this a = m2 and b = n2m
(m2n2m)2=(m2)22(m2)(n2m)+(n2m)2
= m42m3n2+n4m2
Now, m42m3n2+n4m2 + 2m3n2
= m4+n4m2

Question:5(i) Show that

(3x+7)284x=(3x7)2

Answer:

L.H.S. = (3x+7)284x=9x2+42x+4984x

=9x242x+49

=(3x7)2

= R.H.S.

Hence it is prooved

Question:5(ii) Show that

(9p5q)2+180pq=(9p+5q)2

Answer:

L.H.S. = (9p5q)2+180pq=81p290pq+25q2+180pq (Using (ab)2=a22ab+b2 )

=81p2+90pq+25q2

=(9p+5q)2 ((a+b)2=a2+2ab+b2)

= R.H.S.

Question:5(iii) Show that.

(43m34n)2+2mn=169m2+916n2

Answer:

First we will solve the LHS :

=(43m34n)2+2mn=169m22mn+916n2+2mn

or =169m2+916n2

= RHS

Question:5(iv) Show that.

(4pq+3q)2(4pq3q)2=48pq2

Answer:

Opening both brackets we get,

(4pq+3q)2(4pq3q)2=16p2q2+24pq2+9q2(16p2q224pq2+9q2)

=16p2q2+24pq2+9q216p2q2+24pq29q2)

=48pq2

= R.H.S.

Question:5(v) Show that

(ab)(a+b)+(bc)(b+c)+(ca)(c+a)=0

Answer:

Opening all brackets from the LHS, we get :

(ab)(a+b)+(bc)(b+c)+(ca)(c+a)= a2+ababb2+b2+bcbcc2+c2+caaca2

=0 = RHS

Question:6(i) Using identities, evaluate.

712

Answer:

We will use the identity:

(a+b)2=a2+2ab+b2

So, 712=(70+1)2=702+2(70)(1)+12

=4900+140+1

=5041

Question:6(ii) Using identities, evaluate.

992

Answer:

Here we will use the identity :

(ab)2=a22ab+b2

So : 992=(1001)2=10022(100)(1)+12

or =10000200+1

=9801

Question:6(iii) Using identities, evaluate.

1022

Answer:

Here we will use the identity :

(a+b)2=a2+2ab+b2

So :

1022=(100+2)2=1002+2(100)(2)+22

or =10000+400+4

=10404

Question:6(iv) Using identities, evaluate.

9982

Answer:

Here we will the identity :

9982=(10002)2=100022(1000)(2)+22

or =10000004000+4

or =996004

Question:6(v) Using identities, evaluate.

5.22

Answer:

Here we will use :

(a+b)2=a2+2ab+b2

Thus

(5.2)2=(5.0+0.2)2=52+2(5)(0.2)+(0.2)2

or =25+2+0.04

=27.04

Question:6(vi) Using identities, evaluate.

297×303

Answer:

This can be written as :

297×303=(3003)×(300+3)

using (ab)(a+b)=a2b2

or =900009

=89991

Question:6(vii) Using identities, evaluate.

78×82

Answer:

This can be written in form of :

78×82=(802)×(80+2)

or =80222 (ab)(a+b)=a2b2

or =64004=6396

Question:6(viii) Using identities, evaluate.

8.92

Answer:

Here we will use the identity :

(ab)2=a22ab+b2

Thus :

8.92=(90.1)2=922(9)(0.1)+0.12

or =811.8+0.01

or =79.21

Question:6(ix) Using identities, evaluate.

10.5×9.5

Answer:

This can be written as :

10.5×9.5=(10+0.5)×(100.5)

or =1020.52 (a+b)(ab)=a2b2

or =1000.25

or =99.75

Question:7(i) Using a2b2=(a+b)(ab) , find

512492

Answer:

We know,

a2b2=(a+b)(ab)

Using this formula,

512492 = (51 + 49)(51 - 49)

= (100)(2)

= 200

Question:7(ii) Using a2b2=(a+b)(ab) , find

(1.02)2(0.98)2

Answer:

We know,

a2b2=(a+b)(ab)

Using this formula,

(1.02)2(0.98)2 = (1.02 + 0.98)(1.02 - 0.98)
= (2.00)(0.04)

= 0.08

Question:7(iii) Using a2b2=(a+b)(ab) , find.

15321472

Answer:

We know,

a2b2=(a+b)(ab)

Using this formula,

15321472 = (153 - 147)(153 +147)

=(6) (300)

= 1800

Question:7(iv) Using a2b2=(a+b)(ab) , find

12.127.92

Answer:

We know,

a2b2=(a+b)(ab)

Using this formula,

(1.02)2(0.98)2 = (1.02 + 0.98)(1.02 - 0.98)

= (2.00)(0.04)

= 0.08

Question:8(i) Using (x+a)(x+b)=x2+(a+b)x+ab 103×104

Answer:

We know,

(x+a)(x+b)=x2+(a+b)x+ab

Using this formula,

103×104 = (100 + 3)(100 + 4)

Here x =100, a = 3, b = 4

103×104 =1002+(3+4)100+(3×4)

=10000+1200+12

= 11212

Question:8(ii) Using (x+a)(x+b)=x2+(a+b)x+ab , find

5.1×5.2

Answer:

We know,

(x+a)(x+b)=x2+(a+b)x+ab

Using this formula,

5.1×5.2 = (5 + 0.1)(5 + 0.2)

Here x =5, a = 0.1, b = 0.2

5.1×5.2 =52+(0.1+0.2)5+(0.1×0.2)

=25+1.5+0.02

= 26.52

Question:8(iii) Using (x+a)(x+b)=x2+(a+b)x+ab , find

103×98

Answer:

We know,

(x+a)(x+b)=x2+(a+b)x+ab

Using this formula,

103×98 = (100 + 3)(100 - 2) = (100 + 3){100 + (-2)}

Here x =100, a = 3, b = -2

103×98 =1002+(3+(2))100+(3×(2))

=10000+1006

= 10094

Question: 8(iv) Using (x+a)(x+b)=x2+(a+b)x+ab , find

9.7×9.8

Answer:

We know,

(x+a)(x+b)=x2+(a+b)x+ab

Using this formula,

9.7×9.8 = (10 - 0.3)(10 - 0.2) = {10 + (-0.3)}{10 + (-0.2)}

Here x =10, a = -0.3, b = -0.2

9.7×9.8 =102+((0.3)+(0.2))10+((0.3)×(0.2))

=1005+0.06

= 95.

NCERT Solutions for Class 8 Maths Chapter 9 Algebraic Expressions and Identities - Topics

  • What are Expressions?
  • Terms, Factors and Coefficients
  • Monomials, Binomials,f and Polynomials
  • Like and Unlike Terms
  • Addition and Subtraction of Algebraic Expressions
  • Multiplication of Algebraic Expressions: Introduction
  • Multiplying a Monomial by a Monomial
  • Multiplying two monomials
  • Multiplying three or more monomials
  • Multiplying a Monomial by a Polynomial
  • Multiplying a monomial by a binomial
  • Multiplying a monomial by a trinomial
  • Multiplying a Polynomial by a Polynomial
  • Multiplying a binomial by a binomial
  • Multiplying a binomial by a trinomial
  • What is an Identity?
  • Standard Identities
  • Applying Identities

NCERT Solutions for Class 8 Maths - Chapter Wise

NCERT Solutions for Class 8 - Subject Wise

Some Important Identities From NCERT Book for Class 8 Chapter 9 Algebraic Expressions And Identities

  • (a+b)2=(a2+2ab+b2)

you can write

(a+b)2=(a+b)(a+b)

Can be simplified as follows

(a+b)(a+b)=a×a+a×b+a×b+b×b

Now add each term

a×a+a×b+a×b+b×b=a2+ab+ab+b2

=a2+2ab+b2

(a+b)2=(a2+2ab+b2)

  • (ab)2=(a22ab+b2)
  • (ab)(a+b)=a2b2
  • (x+a)(x+b)=x2+(a+b)x+ab

You can form the above identities by yourself. These above identities have been used in many problems of NCERT solutions for class 8 maths chapter 9 algebraic expression and identities.

Also Check NCERT Books and NCERT Syllabus here

Frequently Asked Questions (FAQs)

1. What are the important topics of NCERT syllabus chapter Algebraic Expressions and Identities ?

Addition and subtraction of the algebraic expression, multiplication of the algebraic expression, standard identities, and application of identities are important topics in this chapter.

2. Does CBSE class maths is tough ?

CBSE class 8 maths is not tough at all. It teaches a very basic and simple maths.

3. How many chapters are there in the CBSE class 8 maths ?

There are 16 chapters starting from rational number to playing with numbers in the CBSE class 8 maths.

4. Where can I find the complete solutions of NCERT for class 8 ?

Here you will get the detailed NCERT solutions for class 8 by clicking on the link.

5. Where can I find the complete solutions of NCERT for class 8 maths ?

Here you will get the detailed NCERT solutions for class 8 maths by clicking on the link.

6. Which is the official website of NCERT ?

NCERT official is the official website of the NCERT where you can get NCERT textbooks and syllabus from class 1 to 12.

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A block of mass 0.50 kg is moving with a speed of 2.00 ms-1 on a smooth surface. It strikes another mass of 1.00 kg and then they move together as a single body. The energy loss during the collision is

Option 1)

0.34\; J

Option 2)

0.16\; J

Option 3)

1.00\; J

Option 4)

0.67\; J

A person trying to lose weight by burning fat lifts a mass of 10 kg upto a height of 1 m 1000 times.  Assume that the potential energy lost each time he lowers the mass is dissipated.  How much fat will he use up considering the work done only when the weight is lifted up ?  Fat supplies 3.8×107 J of energy per kg which is converted to mechanical energy with a 20% efficiency rate.  Take g = 9.8 ms−2 :

Option 1)

2.45×10−3 kg

Option 2)

 6.45×10−3 kg

Option 3)

 9.89×10−3 kg

Option 4)

12.89×10−3 kg

 

An athlete in the olympic games covers a distance of 100 m in 10 s. His kinetic energy can be estimated to be in the range

Option 1)

2,000 \; J - 5,000\; J

Option 2)

200 \, \, J - 500 \, \, J

Option 3)

2\times 10^{5}J-3\times 10^{5}J

Option 4)

20,000 \, \, J - 50,000 \, \, J

A particle is projected at 600   to the horizontal with a kinetic energy K. The kinetic energy at the highest point

Option 1)

K/2\,

Option 2)

\; K\;

Option 3)

zero\;

Option 4)

K/4

In the reaction,

2Al_{(s)}+6HCL_{(aq)}\rightarrow 2Al^{3+}\, _{(aq)}+6Cl^{-}\, _{(aq)}+3H_{2(g)}

Option 1)

11.2\, L\, H_{2(g)}  at STP  is produced for every mole HCL_{(aq)}  consumed

Option 2)

6L\, HCl_{(aq)}  is consumed for ever 3L\, H_{2(g)}      produced

Option 3)

33.6 L\, H_{2(g)} is produced regardless of temperature and pressure for every mole Al that reacts

Option 4)

67.2\, L\, H_{2(g)} at STP is produced for every mole Al that reacts .

How many moles of magnesium phosphate, Mg_{3}(PO_{4})_{2} will contain 0.25 mole of oxygen atoms?

Option 1)

0.02

Option 2)

3.125 × 10-2

Option 3)

1.25 × 10-2

Option 4)

2.5 × 10-2

If we consider that 1/6, in place of 1/12, mass of carbon atom is taken to be the relative atomic mass unit, the mass of one mole of a substance will

Option 1)

decrease twice

Option 2)

increase two fold

Option 3)

remain unchanged

Option 4)

be a function of the molecular mass of the substance.

With increase of temperature, which of these changes?

Option 1)

Molality

Option 2)

Weight fraction of solute

Option 3)

Fraction of solute present in water

Option 4)

Mole fraction.

Number of atoms in 558.5 gram Fe (at. wt.of Fe = 55.85 g mol-1) is

Option 1)

twice that in 60 g carbon

Option 2)

6.023 × 1022

Option 3)

half that in 8 g He

Option 4)

558.5 × 6.023 × 1023

A pulley of radius 2 m is rotated about its axis by a force F = (20t - 5t2) newton (where t is measured in seconds) applied tangentially. If the moment of inertia of the pulley about its axis of rotation is 10 kg m2 , the number of rotations made by the pulley before its direction of motion if reversed, is

Option 1)

less than 3

Option 2)

more than 3 but less than 6

Option 3)

more than 6 but less than 9

Option 4)

more than 9

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