Question

How many grams of $Na$ are present in $30$ g $NaOH$?

• A. $10$ g
• B. $15$ g
• C. $17$ g
• D. $20$ g
• E. $22$ g

Answer 1

The correct option is C $17$ g

The molecular weight of $NaOH$ is 40 g/mol.
30 g of $NaOH$ corresponds to $\frac{30}{40}=0.75$ moles.
0.75 moles of $NaOH$ contains 0.75 moles of $Na$.
The atomic mass of $Na$ is 23 g/mol.
0.75 moles of $Na$ corresponds to $23\times 0.75=17$ g of $Na$.