JEE Main · 2021 · 27 Aug 2021 · Shift 2 · Some Basic Concepts of Chemistry

100 g of propane is completely reacted with 1000 g of oxygen. The mole fraction of carbon dioxide in the resulting mixture is

x \times 1 0^{- 2}

. The value of

x

is ____. (Nearest integer)
[Atomic weight :

H = 1.008; C = 12.00; O = 16.00

]

Answer: 19

Solution

Combustion follows

C_{3} H_{8} + 5 O_{2} ⟶ 3C O_{2} + 4 H_{2} O

. The amounts are

100/44 = 2.27

mol propane and

1000/32 = 31.25

mol oxygen; since

2.27

mol propane needs only

11.36

mol oxygen, propane is limiting. This yields

3 \times 2.27 = 6.82

mol

C O_{2}

and

4 \times 2.27 = 9.09

mol

H_{2} O

and leaves

31.25 - 11.36 = 19.89

mol

O_{2}

. The total is

6.82 + 9.09 + 19.89 = 35.8

mol, so the mole fraction of carbon dioxide is

6.82/35.8 = 0.19

, giving

x = 19

JEE Main · 2021 · 27 Aug 2021 · Shift 2 · Integer answer