Question

How many moles of water (H2O) are present in a beaker containing 45.9 g H2O? Give your answer to the correct number of significant figures.
(Molar mass of water = 18.02 g/mol) 45.9 g H2O = mol H2O

Answer 1

Explanation:

Number of moles is defined as the mass of given sample divided by the molar  mass of sample.

Mathematically,      No. of moles = $\frac{mass given}{Molar mass}$

Since, it is given that mass of water is 45.9 g and it is known that molar mass of water is 18.02 g/mol.

Therefore, calculate the number of moles as follows.

               No. of moles = $\frac{mass given}{Molar mass}$

                                     = $\frac{45.9 g}{18.02 g/mol}$

                                     = 2.547 mol

Thus, we can conclude that there are 2.547 mol present in 45.9 g of water.

Answer 2

The moles of water present in a beaker containing $\bold{ 45.9 g H_2O}$ is 2.547 mol.

What are moles?

The mole is the amount of substance of a system which contains as many elementary entities as there are atoms in 0.012 kilogram of carbon 12.

Its symbol is “mol”.

1 mol is equals to $\bold{ 6.02214076 \times 10^2^3}$

Given, the molar mass of water is 18.02 g/mol

Mass of water is 45.9 g

$\bold{Number\;of \;Moles = \dfrac{ mass\; of \;compound}{molar \;mass} }$

$\bold{Number\;of \;Moles = \dfrac{ 45.9\;g}{ 18.02} = 2.547\;mol\; }$

Thus, the number of moles of water is 2.547 mol.

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