Question

How many grams of O2(g) are needed to completely burn 94.4 g of C3H8(g)?

Answer 1

Molar mass:

O₂ = 16 x 2 = 32.0 g/mol    

C₃H₈ = 12 x 3 + 1 x 8 = 44.0  g/mol

Balancing chemical equation :

C₃H₈+ 5 O₂ = 3 CO₂ + 4 H₂O

44.0 g C₃H₈ ------------- 5 x 32.0 g O₂
94.4 g C₃H₈-------------- ( mass of O₂)

mass of O₂ = 94.4 x 5 x 32.0 / 44

mass of O₂ = 15104 / 44

= 343.27 g of O₂

hope this helps!