Question

(i) A molten metal weighing 150 g is kept at its melting point 800°C. When it is allowed to solidify at the same temp, it gives out 75000 J of heat. What is the specific heat of the metal?

(ii) If its specific heat capacity is 200 J/kgK? How much additional heat will it give out in cooling to -50°C?

Answer 1

Let the specific latent heat of metal is L.

(i) When the metal is allowed to solidify at its m.p./ i.e., 800°C, it will give out its latent heat only.

Therefore mL = 75000

or 0.150 × L = 75000

∴ L = `75000/1150` = 65217.3 J/Kg.

(ii) Heat given out by the metal piece in cooling down to - 50°C. Fall in temperature of the metal piece =[800 - (-50)] = 850°

∴ Heat given out = m × s × t = (0.150 × 200 × 850) J

= 25500 joule