Question

Some hot water was added to 3 times its mass of cold water at 10 degree celsius and the resulting temperature was found to be 20 degrees celsius . What was the temperature of hot water ?

Answer 1

Answer:

50°C

Explanation:

as hot water reduced heat,so the -ve sign comes.

Answer 2

Answer:

50°C

Explanation:

Let the temperature of hot water be t°C and mass of hot water = m

∴ Mass of cold water = 3 gm

Temperature of cold water = 10°C

Final temperature of mixture = 20°C

Heat taken by cold water = 3 * C * (20 - 10) [∵ mc ΔQ₁]

Heat given by hot water = m * C * (t - 20)

Heat given = Heat taken

m * C * (t - 20) = 3 * C * 10

⇒ t - 20 = 30

∴ t  = 30 + 20 = 50°C

Therefore,

Temperature of hot water = 50°C

Hope it helps!