A substance contains 35.0 g nitrogen, 5.05 g hydrogen, and 60.0 g of oxygen. How many grams of hydrogen are there in a 142-g sample of this substance?

1 Answer
Apr 12, 2017

There will be 7.17 g of hydrogen in the 142-g sample.


We need to dtermine what is known as the "percent composition by mass" for this compound. Then, the portion of a larger sample can be found.

The total mass of the three elements is 100.05 g, which means that the percentages are virtually the same as the given masses:

% N = #35.0/100.05 xx 100# = 34.98 %

% H = #5.05/100.05 xx 100# = 5.047 %

% O = #60.0/100.05 xx 100# = 59.97 %

While only the middle value is required, it is worthwhile to find all three in the event that we need the other information in a follow-up problem.

Since 5.047 % of the mass is due to hydrogen, we can now multiply this percentage by any otherr mass:

0.05047 xx 142 = 7.17 g of hydrogen