Question

What is the mass of a mole of water containing 50% of heavy water $\left(D_{2}O\right)$ ?

• A. $19g$
• B. $18g$
• C. $20g$
• D. $21g$

Answer 1

The correct option is A $19g$

A mole of water containing 100 % of $H_{2}O$ weighs $2\left(1\right)+16=18$ g.

A mole of water containing 100 % of $D_{2}O$ weighs $2\left(2\right)+16=20$ g.

A mole of water containing 50 % of $H_{2}O$ and 50 % of $D_{2}O$ weighs $\frac{18+20}{2}=19$ g.