A copper vessel of mass 100 g contains 150 g of water at 50°C

A copper vessel of mass 100 g 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 J g^-1 ⁰C^-1
Specific heat capacity of water = 4.2 J g^{-1 ⁰C}-1
Specific latent heat of fusion of ice = 336 J g^-1

Answer

m c θ + m c θ = m I L + mi c θ

100 x 0.4 x 45 + 150 x 4.2 x 45 = mi ( 336 + 4.2 x 5 )

m_i = 84.45 g