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?

Answer 1

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.