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Steam is added to 100 g of water to raise its temperature from 24 deg C to 90 deg C. Calculate the mass of steam required. (Latent heat of steam = 540 cal/g, specific heat of water = 1 cal/g/deg C; steam condenses at 100 deg C and the condensed water cools to 90 deg C.)

1. 10 g
2. 12 g
3. 15 g
4. 20 g

Correct answer: 12 g

Solution

Equating heat gained by water (6600 cal) to heat released by steam (550 cal per gram) gives about 12 g of steam.

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