Question

Suppose 7.8 kg of a solid substance is at its melting point of 38°c. if the latent heat of fusion is 237,532 j/kg, calculate the change of the substance's entropy when it melts.

Answer 1

To find the change in entropy when 7.8 kg of a substance melts, first convert the melting point to Kelvin, calculate heat absorbed using Q = m * Lf, and then use ΔS = Q/T to get an increase in entropy of 5,953 J/K.

Step-by-step explanation:

The question is asking to calculate the change in entropy when 7.8 kg of a solid substance melts at its melting point using given values of mass, melting point, and the latent heat of fusion. The change in entropy (ΔS) during melting can be calculated using the formula ΔS = Q/T, where Q is the heat absorbed (which can be calculated using Q = mLf, with m as the mass and Lf as the latent heat of fusion) and T is the absolute temperature in Kelvin.

First, we need to convert the melting point from Celsius to Kelvin:

• 38°C + 273.15 = 311.15 K

Then, we calculate the total heat absorbed:

• Q = (7.8 kg)(237,532 J/kg) = 1,852,749.6 J

Now, we find the change in entropy:

• ΔS = Q/T = 1,852,749.6 J / 311.15 K = 5,953 J/K

Therefore, the entropy increases by 5,953 J/K when the substance melts at 38°C.