Question

What should be the temperature of 1g of ice, so that when it’s added to 9g of water, lowers the temperature of water by 10°C?  Sw = 1cal/ g°C, Sice = 0.5cal/ g°C, Lfus= 80cal/g.

(a) 20°C

(b) -20°C

(c) 0°C

(d) 10°C

I got this question by my college professor while I was bunking the class.

The above asked question is from Thermal Properties of Matter in chapter Thermal Properties of Matter of Physics – Class 11

Answer 1

Correct answer is (b) -20°C

For explanation: Let the initial temperature of ice be T°C.                                                                                              Heat lost by ice will be the same as the heat lost by water.  

∴ 1*0.5*(0-T) + 1*80 = 9*1*10                                                                                                          ⇒ T = -20°C.