Question

What entropy change is associated with the reversible phase change from 1.0kg of ice to water at 0 ° C?

Answer 1

1200 J/K

Step-by-step explanation:

The formula for the entropy associated with a reversible phase change is

`\Delta S= \frac{q_{\text{rev}}}{T}`

For a reversible phase change like melting,

`q_{\text{rev}} = m\Delta_{\text{fus}}H`

Data:

Mass of ice = 1.0 kg

T = 0 °C

Calculations

1. Convert the mass of ice to grams

`\text{Mass of ice} = \text{1.0 kg } * \frac{\text{1000 g}}{\text{1 kg}} = \text{1000 g}`

2. Convert the temperature to kelvins

T = (0 + 273.15) K = 273.15 K

3. Calculate the heat needed to melt the ice

`q_{\text{rev}} = m\Delta_{\text{fus}}H = \text{1000 g} * \frac{\text{334 J}}{\text{1 g}} = \text{334 000 J}`

4. Calculate the entropy change

`\Delta S = \frac{q_{\text{rev}}}{T} = \frac{\text{334 000 J}}{\text{273.15 K}} = \textbf{1200 J/K}`