Question

200 g of ice at 0 °C converts into water at 0°C in 1 minute when heat is supplied to it at a constant rate. In how much time, 200 g of water at 0°C will change to 20°C ? Take specific latent heat of ice = 336 J g^-1.

Answer 1

Heat required to convert 200 g of ice at 0°C to 200 g of water at 0°C = mL

m = 200 g = 200 × 336,

L = 336 J g^- = 67200 J

Time = 1 min = 60 sec

Heat produced in 1 sec = `67200/60 = 1120` J

Now heat required to change 200 g of water at 0°C to 200 g of water at 20°C

= mc (t - 0)

= 200 × 4.2 (20 - 0)

= 200 × 4.2 × 20

= 16800 J

1120 J is produced in 1 sec.

16800 J is produced in `16800/1120` = 15 sec