What is the minimum amount of heat needed to completely melt 200 g of silver(melting point=1235 K; c=236J/kg K; Lf=105kJ/kg)at 250 degree C?
- Steve4PhysicsLv 76 years agoFavorite Answer
250°C = (250 + 273 K) = 523 K
200g = 0.2kg
First find the heat needed (Q1) to raise the silver from 523K to its melting point (1235K):
Q1 = m.c.ΔT = 0.2 x 236 x (1235 - 523)
Note Lf = 105kJ/kg = 105,000J/kg. The heat needed to melt the silver (Q2) is:
Q2 = m.Lf = 0.2 x 105,000
Then add Q1 and Q2.