What is percentage composition?

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Answer 1 · 2016-07-05T08:47:17

"Percentage composition is the percentage by mass of each element present in a compound" - www.chemteam.info

An example of this follows:

Find the percentage compositions of carbon and hydrogen in methane, #CH_4.#
#M_R(CH_4)=16.0gmol^-1#

Mass of 1 mol of methane:
#m(CH_4)=nM=1.00mol*16.0gmol^-1=16.0g#

Mass of hydrogen in 1 mol of methane:
#m(H)=nM=4.00mol*1.00gmol^-1=4.00g#

Mass of carbon in 1 mol of methane:
#m(C)=nM=1.00mol*12.0gmol^-1=12.0g#

Percentage mass of hydrogen in 1 mol of methane:
#=(4.00g)/(16.0g)*100%=25%#

Percentage mass of carbon in 1 mol of methane:
#=(12.0g)/(16.0g)*100%=75%#

Percentage composition of methane:
#25% H, 75% C#