Calculate the number of kJ of heat necessary to raise the temperature of 60.0 g of aluminium from 35°C to 55°C. Molar heat capacity of Al is 24 J mol–1 K–1.
From the expression of heat (q),
q = m. c. ΔT
c = molar heat capacity
m = mass of the substance
ΔT = change in temperature
Substituting the values in the expression of q:
`q = (60/27 mol)(24 J mol^(-1) K^(-1))(20K)`
q = 1066.7 J
q = 1.07 kJ
No. of moles of Al (m) = (60g)/(27 g mol-1) = 2.22 mol
Molar heat capacity (C) = 24 J mol-1 K-1.
Rise in temperature (∆T) = 55 – 35 = 20°C = 20 K
Heat evolved (q) = C x m x T = (24 J mol-1 K-1) x (2.22 mol) x (20 K)
= 1065.6 J = 1.067 kj