What mass of hydrogen is in a 102.0 g quantity of methane (CH4)?
A.1.01 g H
B.2.57 g H
C.4.0 g H
D.25.7 g H

Question

What mass of hydrogen is in a 102.0 g quantity of methane (CH4)? 
A.1.01 g H
B.2.57 g H
C.4.0 g H
D.25.7 g H

anonymous · Answer

Could anybody please show me how to do this? Please?

anonymous · Answer

D is your answer feel free to award the medal of honor if you find me to be worthy!!!!!!!!!!!!!!!!!!!!!!!

gitface · Answer

Determine the total molar mass of methane. I calculated 16.042 g/mol, using a value of 12.01 g/mol for Carbon and 1.008 g/mol for Hydrogen. Then determine what percent of the total molar mass the hydrogen contributes.

Total molar mas = 16.052 g/mol
Molar mass of hydrogen in methane = 4 x 1.008 g/mol = 4.032 g/mol

%H in CH4 = (molar mass H/total molar mass) x 100 = 4.032 / 16.042 = 25.13%

Then determine 25.13% of your total mass.

102.0g x .2513 (decimal form of 25.13%) = 25.6326 g.

Rounding to your 3 sigfigs you get 25.6 g. This value is closest to D. The difference is caused by my value for the molar mass of hydrogen. If you use a value of 1.01 g/mol for the molar mass of hydrogen, you get 25.674 g as your answer, which roudns to 25.7g.