Percentage Mass of Elements in Compounds

The only formulas you need are:
Molar Mass: G/Mol and Molar Volume: L/Mol
That is basically it and now here are some examples to practice.

EXAMPLE 1:

Calculate the percentage of each element in C3H8.
Step 1: Formula used should be molar mass: G/Mol.
Step 2: Find the molar mass of each element.
Carbon: 3(12.0) + Hydrogen: 8(1)= 44g/mol
To find the percentage divide one of the element's molar mass by the total molar mass of the compound.
Step 3: Carbon: 36g/mol/44g/mol= .818 x 100= 82.0%. Hydrogen: 8g/mol/44g/mol= .181 x 100=18%

EXAMPLE 2:
Find the percent mass of XeF2
Step 1: Use formula molar mass: G/Mol
Step 2: Find molar mass of each element.
Xenon: 131.1 + Flourine: 2(19.0)= 38 = 169.1
Step 3: Divide individual molar mass by total molar mass.
Xenon: 131.1/169.1= .775 = 78% Flourine: 38/169.1=.2247 = 22%