Question

A cylinder of cooking gas supplied by indian oil corporation is assumed to contain 14 kg of butane (∆hc for c4h10 = - 2600 kj mol-1 ). if a small family of three persons, requires 10,000 j of heat energy per day for cooking, the gas in the cylinder would last for

Answer 1

Butane formula is C4H10

Molar mass = 12x4 + 10 = 58

Moles of butane in 14kg (14000g) = 14000/58 = 241.38

Amount of heat that can be obtained from this number of moles

                            = 241.38 x 2600 kJ

                            = 627.59kJ = 627590J

No. of days = 627590/10000

                   = 62.759 days

Answer 2

Butane = C₄H₁₀

Molecular mass of butane :

12 × 4 + 1 × 10 = 58 g/mole

The mass of butane = 14kg

Convert to grams : 14 × 1000 = 14000g

The number of moles in 14000g :

Moles = mass / molar mass

14000 / 58 = 241.38 moles

ΔH = - 2600kJ/mole

1 mole = - 2600 kilojoules (the negative sign indicate that it's an exothermic reaction, so we ignore the sign in the calculations)

The total ΔH = 2600 × 241.38 = 627588 kJ

In one day the family uses = 10000 joules

Convert this to kilojoules by Dividing by 1000:

10000/1000 = 10kJ

10kJ = 1 day

627588kJ =?

By cross multiplication we have :

627588 / 10 × 1 = 62758.8 days

Answer = 62758.8 days