Question 3A molten metal of mass 150 g is kept at it's melting point 800° C. When it is allowed to freeze at the same temperature, it gives out 75,000 J of heat energy.(a) What is the specific latent heat of the metal?(b) If the specific heat capacity of metal is 200 J kg-1 K-1, how much additional heat energy will the metal give out in cooling to - 50° C?

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Accepted Answer

(a) Given,Mass (m) = 150 gHeat energy given out (Q) = 75,000 JSpecific latent heat of the metal = ?From relation Q = m x LSubstituting the values in the formula we get,75000=150×L⇒L=75000150⇒L=500 J g−175000 = 150 \times L \[0.5em] \Rightarrow L = \dfrac{75000}{150} \[0.5em] \Rightarrow L = 500 \text{ J g}^{-1} \[0.5em]75000=150×L⇒L=15075000​⇒L=500 J g−1Hence, the specific latent heat of the metal = 500 J g-1(b) Specific heat capacity of metal is 200 J kg-1 K-1Change in temperature= 800 – (-50) = 800 + 50 = 850° C = 850 KFrom relation,Q = m x c x change in temperatureSubstituting the values we get,Q=0.15×200×850Q=25,500JQ = 0.15 \times 200 \times 850 \[0.5em] Q = 25,500 J \[0.5em]Q=0.15×200×850Q=25,500JHence, 25,500 J of heat energy will be given out

Calorimetry — Question 3

Question 3