An experiment takes 10 minutes to raise the temperature of water in a container from 0°C to 100°C and another 55 minutes to convert it totally into steam by a heater supplying heat at a uniform rate. Neglecting the specific heat of the container and taking specific heat of water to be 1 cal/g°C, the heat of vaporization according to this experiment will come out to be 530 cal/g, 540 cal/g, 550 cal/g, or 560 cal/g?

Assuming heater is supplying heat at uniform rate of ΔQ cal/s
In 10 minutes total heat transferred = 600 × ΔQ
This amount should be equal to heat gained by water = mcΔT
where m is mass of water and c is specific heat capacity of water.
mcΔT = 600ΔQ
m × 1 cal/g°C × (100°C) = 600ΔQ
⇒ ΔQ = m/6.. (i)
The heater supplies heat at constant temperature to convert water into steam, the amount of heat is given by
55 minutes × 60 × sec × ΔQ. (i)
this amount should be equal to heat gained by water to convert into steam at constant temperature = mL
where L is latent heat of vaporization
3300ΔQ = mL.. (ii)
substituting value of ΔQ from equation (i)
3300m/6 = mL
L = 550 cal/g
Hence correct answer is option B