how to find the percent composition by mass of $\text C_8 \text H_8$

Question

lgbasallote · Answer

would appreciate @waterineyes 's expertise

anonymous · Answer

I have to go now...

lgbasallote · Answer

that's convenient

lgbasallote · Answer

@mathslover are you a chemslover too?

mathslover · Answer

oh k .. so wait

mathslover · Answer

percent composition by mass of C and H both ?

mathslover · Answer

first of all:

mass of C = 12 (approx.) 

            H = 1 

so mass of C_8 = 12*8 = 96 g

 and that of H_8 = 1* 8 = 8 g

mathslover · Answer

total mass = 104 g 

percent composition of mass of C in C_8 H_8 = $\large{\frac{96}{104}*100 }$ = 92.3 % 


percent composition of mass of H in C_8 H_8 = $\large{\frac{8}{104}*100}$ = 7.7 %

mathslover · Answer

got it?

lgbasallote · Answer

well i know the mass percent of the elements...what intrigues me is the mass % of the compound

mathslover · Answer

% composition by mass of a compound means :

mass % of the element in the compound..

lgbasallote · Answer

just that?

mathslover · Answer

though .. @Xishem can confirm me .. if you want confirmation ..

mathslover · Answer

may be m wrong somewhere

lgbasallote · Answer

interestiing

lgbasallote · Answer

it seems there's more to this

xishem · Answer

What mathslover said seems accurate.

It's as simple as converting from moles of each element to mass of each element and dividing each part of the mass by the total mass.

The percent composition of the compound IS the percent of carbon by mass as well as the percent of hydrogen by mass.

I'm unsure what you are uncertain about.

lgbasallote · Answer

well what i am unsure about is this http://openstudy.com/updates/5039df93e4b043c156a326fd idk if you really use this method in that question...or it was just a coincidence