Question

A 45g aluminium spoon at 24 degree Celsius is placed in180ml of coffee at 85 degree Celsius and the temperature of the two becomes equal

Answer 1

when Heat lost by coffee -q= m( coffee) * C (coffee) * ΔT

and Heat gained by spoon q = m (spoon) * C (spoon) * ΔT

when q = -q  

∴ m(coff)* C(coff) * ΔT (coff) = m(sp)* C(sp)*ΔT(sp)

when the final tempreature of both will be the same so,

m(coff) * C(coff) * ( Tf - Ti(coff)) = m(sp) * C(sp) * (Tf- Ti(sp)

by substitution:

note: as the coffe will reduce heat so, ΔT = (85-Tf)

and the spoon will gain heat so ΔT = (Tf-24)

180 g * 4.186 * (85-Tf) = 45 * 0.88 * (Tf- 24)

∴Tf = 81 °C