0.5 kg of lemon squash at 30∘C is placed in a refrigerator which can remove heat at an average rate of 30 J s−1.How long will it take to cool the lemon squash to 5∘C? Specific heat capacity of squash=4200 J kg−1 K−1.
Given,
Mass of lemon squash, m=0.5 kg
Specific heat capacity of lemon squash= 4200 J kg−1 K−1
Fall in temperature, θ= 30−5=25 deg Celsius
Heat extracted by the refrigerator, H=mCθ
=0.5×4200×25=52500 J
Rate of extraction of heat=30J/s
Time in which lemon squash cools=52500/30=1750 sec or 29.17 min