How much heat is needed to melt 2 kg of lead taken at 270C?
| September 23, 2021 | education
Q = Q1 + Q2.
Q1 = C * m * (tк – tн), where C – specific heat (С = 130 J / (К * kg)), m – mass (m = 2 kg), tк – melting point (tк = 327 ºС) , tн – initial temperature (tн = 270 ºС).
Q1 = C * m * (tк – tн) = 130 * 2 (327 – 270) = 14820 J.
Q2 = λ * m, where λ is the specific heat of fusion (λ = 0.25 * 10 ^ 5 J / kg).
Q2 = (0.25 * 10 ^ 5) * 2 = 50,000 J.
Q = Q1 + Q2 = 14820 + 50,000 = 64820 J = 64.82 kJ.
Answer: To melt lead, you need to spend 64.82 kJ of energy.
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