Question

A 403.0-kg copper bar is melted in a smelter. The initial temperature of the copper is 320.0 K. How much heat must the smelter produce to completely melt the copper bar? For solid copper, the specific heat is 386 J/kg • K, the heat of fusion is 205 kJ/kg, and the melting point is 1357 K.

Answer 1

The answer is 2.49 x 10^5 KJ. This was obtained (1) use the formula for specific heat to achieve Q or heat then (2) get the energy to melt the copper lastly (3) Subtract both work and the total energy required to completely melt the copper bar is achieved.

Answer 2

2.42 x 10^8 J

Step-by-step explanation:

m = 403 kg

T1 = 320 K

c = 386 J/Kg C

L = 205 kJ / kg = 205000 J/Kg

T2 = 1357 K

Heat used to increase the temperature till 1357 K

H1 = m x c x (T2 - T1)

H1 = 403 x 386 x ( 1357 - 320)

H1 = 1.6 x 10^8 J

Heat used to melt

H2 = m x L

H2 = 403 x 205000 = 8.2 x 10^7 J

Total heat used to melt completely

H = H1 + H2

H = 1.6 x 10^8 + 0.82 x 10^8 = 2.42 x 10^8 J