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Question
Some hot water was added to three times its mass of cold water at 10°C and the resulting temperature was found to be 20°C. What was the temperature of the hot water?
Solution
Let the temperature of hot water be t°C and mass of hot water = m gm
Mass of cold water = 3 gm
Temperature of cold water = 10°C
Final temperature of mixture = 20°C
Heat taken by cold water = 3m × C × (20 - 10)
Heat given by cold water = m × C × (t - 20)
Heat given = Heat taken
m × C × (t - 20) = 3m × C × 10
t - 20 = 30
∴ t = 30 + 20 = 50°C
Time required is 1hr, 7 min, 12 sec.
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