Question

1 kg of molten lead at its melting point of 327°C is dropped into 1 kg of water at 20°C. Assuming no loss of heat, calculate the final temp. of water. (Sp. heat of lead = 130 J/kg°C, latent heat of lead = 27000 J/kg and Sp. heat of water = 4200 J/kg°C).

Answer 1

Let the final temperature of the mixture be t

Heat lost by lead = Heat gained by water

m₁L + m₁ x CL x (327 - t) = m_z x c_w x (t - 20)

1 x 27000 + 1 x 130 x (327 - t) = 1 x 4200 x (t - 20)

27000 + 42510 _ 130t = 4200t - 84000

t = 35.45°C

So, the final temperature of water is 35.45°C.