Introduction

Let's define a "molecule" before determining how many molecules are contained in the 9 grams of water. A molecule is a collection of two or more atoms that are chemically bound together and constitutes the smallest building block of a compound that can take part in a chemical reaction. Any compound's molecular weight must be multiplied by Avogadro's constant to determine its molecular composition.

Number of Molecules = number of moles X 6.023\times 10^{23} …………(i)

Where the number of moles:

It is the proportion of a compound's actual mass to its molecular mass. The following is the expression to determine the number of moles:

n = \frac{m}{M}, …………..(ii)

Here, "m" stands for the given mass of the compound, and "M" stands for the given compound's molar mass.

Calculation

To find out the number of molecules in 9 grams of water:

Given the mass of water molecule = 9 g

The molecular mass of water molecule = 18 g

Using equation (ii), calculate the number of moles of water:

Number of moles, n = \frac{9}{18} = 0.5

Using equation (i), calculate the number of molecules of water:

Number of molecules = n\times 6.023 \10^{23}

\Rightarrow 0.5 \times 6.023 \10^{23}

\Rightarrow 3.01 \times 10^{23}

Conclusion

Hence, the number of molecules in 9 grams of water is 3.01 \times 10^{23} molecules.