Question

Which of the following correctly represents 360 g of water?

• A. 2 moles of water
• B. 20 moles of water
• C. $1.2044\times {10}^{24}$ molecules of water
• D. $1.2044\times {10}^{25}$ molecules of water

Answer 1

Answer: (B), (D)

$1.2044\times {10}^{25}$ molecules of water

We know that,
the mass of one mole of water $\left({\text{H}}_2\text{O}\right)$
={2 $\times$ atomic mass of hydrogen} + {atomic mass of oxygen}
= {2 $\times$ 1} + 16 = 18 g
Number of moles in 360 g of water= $\frac{360}{18}$ = 20 moles.

We know that Avogadro's number = 6.023 $\times {10}^{23}$

Number of molecules in 20 moles of water = Avogrado number $\times$ number of moles
= $6.023\times {10}^{23}\times 20$ = $1.2044\times {10}^{25}$ molecules

$\therefore 1.2044\times {10}^{25}$ molecules and 20 moles are equivalent to 360 g of water.