Question

Which of the following correctly represents $360\mathrm{g}$ of water?

• A. (i)
• B. (i) and (iv)
• C. (ii) and (iii)
• D. (ii) and (iv)

Answer 1

The correct option is D

(ii) and (iv)

Step 1: Calculating the Molar Mass of water

mass of 1 mole of water = molar mass of water =$18\raisebox{1ex}{$\mathrm{g}$}\!\left/ \!\raisebox{-1ex}{$\mathrm{mol}$}\right.$.

Since 1 molecule of water weighs 18 amu, its 1 mole will weigh 18g.

Step 2: Calculating the number of moles in $360\mathrm{g}$ of water

No. of moles = $\frac{givenmass}{Molarmass}$

No. of moles in $360\mathrm{g}$ of water = $\frac{360g}{\left(18{\displaystyle \raisebox{1ex}{$g$}\!\left/ \!\raisebox{-1ex}{$mol$}\right.}\right)}=20mol$

This proves that option (ii) is correct.

Step 3: Calculating the number of molecules in $20\mathrm{mol}$ water:

No. of molecules in 1 mole of water = $6.022\times {10}^{23}$ molecules ($6.022\times {10}^{23}$ is an Avogadro's number)

So in$20\mathrm{mol}$, there will be

$$\begin{gathered} =20\times 6.023\times {10}^{23} \\ =120.44\times {10}^{23} \\ =1.2044\times {10}^{25}molecules \end{gathered}$$

This proves that option (iv) is correct.

Hence, the correct answer is Option D.