Question

if you had 185.42 g of C2H8 (propane), how many moles would you have?

Answer 1

Answer:

molar masses of C

3

H

8

,O

2

,CO

2

are 44g/mol, 32g/mol and 44g/mol respectively.

The number of moles is the ratio of mass to molar mass.

The number of moles of C

3

H

8

=

44g/mol

88g

=2mol

Number of moles of O

2

=

32g/mol

160g

=5mol

2 moles of propane will react with 2×5=10 moles of oxygen, however, only 5 moles of oxygen are present.

Hence, oxygen is the limiting reagent and propane is the excess reagent.

5 moles of oxygen will give 3 moles of CO

2

.

Mass of CO

2

=3 mol×44 g/mol=132 g

Answer 2

Explanation:

given mass= 185.42

molar mass of propane = 2×24+8×1=32

Mole= given mass/molar mass

= 185.42/32

=5.79moles