The constant pressure molar heat capacity, C_{p, m}C p, m , of methane gas, CH_4CH 4 , is 35.31/text{ J K}^{-1}/text{ mol}^{-1}35.31 J K - 1 mol - 1 at temperatures close to 298/text{ K}298 K. Calculate the enthalpy change when 1.6/text{ kg}1.6 kg of methane gas is heated from a temperature of 280/text{ K}280 K to 320/text{ K}320 K.

Constant pressure molar heat capacity Cp = 35.3 J / mol

Enthalpy change of the given process can be calculated as follows

ΔH = n Cp x Δt, n is number of mole, Cp is molar heat capacity and Δt

is change in temperature.ΔH is enthalpy change.

Putting the values

ΔH = n Cp x Δt

mol weight of methane = 16

1.6 kg = 1600 g

= 1600 / 16

= 100 moles

n = 100

Putting the values

ΔH = n Cp x Δt

= 100 x 35.3 x (320 - 280)

= 141200 J

= 141.2 KJ.