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

Answer:

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

Answer:

Surely you mean #1.33*g# of hydrogen..........we eventually get a molecular formula of #H_2O_2#, i.e. #"hydrogen peroxide"#.

Explanation:

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

#"Moles of hydrogen"=(1.33*g)/(1.00794*g*mol^-1)=1.32*mol#

#"Moles of oxygen"=(21.3*g)/(15.999*g*mol^-1)=1.33*mol#

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"}xxn="molecular formula"#

And thus #{1.01+16.0}*g*mol^-1xxn=34.1*g*mol^-1#.

Clearly #n=2#, and thus we gets a molecular formula of #2xx{HO}-=H_2O_2#.