80 gm of water at 30°C is poured on a large block of ice at 0°C. The mass of ice that melts is
Since, the block of ice at 0°C is large, the whole of ice will not melt, hence final temperature is 0°C .
Q1 = heat given by water in cooling upto 0°C
= 2400 cal
If m gm be the mass of ice melted, then
Q2 = mLF = m x 80
Now, Q2 = Q1
m x 80 = 2400 or m = 30 gm.