What is the molecular formula of a substance that decomposes into 133 g of H and 21.3 g of O, and was found to have a molar mass of 34.1 g?

2 Answers
May 19, 2017

error in your question!

Explanation:

from molar mass the logical answer is H2O2 (likely) ...
molar mass is 34
atomic mass of O is 16
atomic mass of H is 1
the only realistic combination of this is 2 x O + 2 x H, H2O2.

From your data you get a weird formula of H99O1 (unlikely) ....enter image source here

May 19, 2017

Surely you mean 1.33g of hydrogen..........we eventually get a molecular formula of H2O2, i.e. hydrogen peroxide.

Explanation:

Let us suppose that there were 1.33g hydrogen, and 21.3g oxygen:

Moles of hydrogen=1.33g1.00794gmol1=1.32mol

Moles of oxygen=21.3g15.999gmol1=1.33mol

And thus we gets an empirical formula of HO.

But we know that the molecular formula is a whole number multiple of the empirical formula:

{empirical formula}×n=molecular formula

And thus {1.01+16.0}gmol1×n=34.1gmol1.

Clearly n=2, and thus we gets a molecular formula of 2×{HO}H2O2.