Question 9(ii)
If a block (made of lead) of mass 500 g at 127°C is heated in a furnace till it completely melts. Determine the quality of heat required.
(a) to bring the block upto its melting point.
(b) total heat energy required to melt the block to its melting point.
(c) total heat energy required.
(Take, melting point of lead = 327°C, specific heat capacity = 0.13 Jg-1°C-1 and specific latent heat of fusion = 26 Jg-1)
(a) Given,
Mass of lead = 500 g
Change in temperature of water = (327 - 127 ) = 200°C
specific heat capacity of lead = 0.13 Jg-1°C-1
specific latent heat of fusion = 26 Jg-1
melting point of lead = 327°C
Amount of heat required to raise its temperature :
mc△t = 500 x 0.13 x 200 = 13000 J = 13 kJ
(b) Heat required to melt the lead = mc = 500 x 26 = 13000 J = 13 kJ
(c) Therefore, total heat required = 13 + 13 = 26 kJ