Question

What is the mass of 4.82 x ${10}^{25}$ molecules of $H_{2}O$ in grams?

• A. 1440.71 g
• B. 1448.71 g
• C. 1438.71 g
• D. 1248.71 g

Answer 1

The correct option is A 1440.71 g

Number of moles of water $=\frac{\text{Total number of molecules}}{\text{Avogadro constant}}=\frac{4.82\times {10}^{25}}{6.022\times {10}^{23}}=80$

Therefore, mass of water = $\text{Number of moles}\times \text{Molecular Mass}$
$=80\times 18=1440.71$ g