Question

A copper vessel of mass 100g contains 150 g of water at 50°C. How much ice is needed to cool it to 5°C ?

Given: Specific heat capacity of copper = 0.4 Jg^–1 °C^–1 Specific heat capacity of water = 4.2 Jg^–1 °C^–1 Specific latent heat of fusion of ice = 336 Jg^–1

Answer 1

(i) Heat given by water to reach 5°C + Heat given by copper vessel to reach 5°C = Heat taken by ice to melt at 0°C + Heat taken by melted ice to reach 5°C. 

mc ∆t + mc ∆t = mL + mc ∆t 

where ∆t = change in temperature 

[150 × 4.2 × (50° – 5°)] + [100 × 0.4 × (50° – 5°)] = (m × 336) + [(m × 4.2 × (5-0)]

(150 × 4.2 × 45) J + (100 × 0.4 × 45) J = (m × 336) J + (m × 4.2 × 5) J 28350 + 1800 = 336m + 21m