Question

A substance contains $35.0g$ nitrogen, $5.05g$ hydrogen, and $60.0g$ oxygen. How many grams of oxygen are there in a $200g$ sample of the substance?

• A. $10.1g$
• B. $60.0g$
• C. $70.0g$
• D. $120g$
• E. $140g$

Answer 1

Answer: (A)

$10.1g$

Add up the masses of $N,H$ and $O$ to find the mass of the compound = $100.05$ grams

You then know that this mass of the compound contains $5.05$g of hydrogen.
So by proportion, you can find how much hydrogen will be in $200$g of the compound

$100.05$ grams of the compound contains $5.05$g hydrogen
$200g$ of the compound contains $\left(5.05/100.05\right)\times 200$g

$=10.1$