A 771.0-kg copper bar is put into a smelter for melting.The initial temperature of the copper is 300.0 K.How much heat must the smelter produce to completely melt the copper bar? The specific heat for copper is 386 J/kg ∙ K,the heat of fusion for copper is 205,000 J/kg,and its melting point is 1357 K. A)4.73 × 10⁵_kJ B)3.15 × 10¹¹_kJ C)3.15 × 10⁸_kJ D)5.62 × 10⁵_kJ

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Quizplus · Accepted Answer

The correct answer is A because the heat required to melt the copper bar is equal to the sum of the heat required to raise the temperature of the copper from 300.0 K to 1357 K and the heat required to melt the copper at 1357 K. The heat required to raise the temperature of the copper is given by:Q1 = m * c * (T2 - T1)where m is the mass of the copper bar, c is the specific heat of copper, T2 is the melting point of copper, and T1 is the initial temperature of the copper.The heat required to melt the copper is given by:Q2 = m * Lfwhere Lf is the heat of fusion of copper.The total heat required to melt the copper bar is:Q = Q1 + Q2Q = m * c * (T2 - T1) + m * LfQ = 771.0 kg * 386 J/kg ∙ K * (1357 K - 300.0 K) + 771.0 kg * 205,000 J/kgQ = 4.73 × 105 kJ

A 7710-Kg Copper Bar Is Put into a Smelter for Melting