Question

What weight of sodium contains the same number of atoms as those in $20$ grams of oxygen?
(Given: Atomic weight of $Na=23u,O=16u$)

• A. $28.75\text{g}$
• B. $31.25\text{g}$
• C. $13.91\text{g}$
• D. $23.16\text{g}$

Answer 1

The correct option is B $31.25\text{g}$

moles of $8$ grams of oxygen $=\frac{20\text{g}}{16\text{g/mol}}=1.25\text{mol}$
Number of moles of sodium will be equal to number of moles of oxygen i.e., $1.25\text{mol}$
Weight of $1.25\text{mol}$ of sodium $=1.25\text{mol}\times 23\text{g/mol}=31.25\text{g}$