Find the entropy change when 51g of steam condenses to water at 100 ∘C.
Physics student
To find the entropy change when steam condenses to water, we need to use the formula:
ΔS = m * ΔH / T
Where:
ΔS = change in entropy
m = mass of the substance (in grams)
ΔH = enthalpy change (in J)
T = temperature (in Kelvin)
First, let's convert the given temperature from Celsius to Kelvin:
T = 100 + 273.15 = 373.15 K
Next, we need to find the enthalpy change, ΔH. The enthalpy change when steam condenses to water is the heat released (or absorbed) during the phase change. This value can be found in a specific heat table or calculated using the heat of vaporization (ΔH_vap) for water:
ΔH = m * ΔH_vap
The heat of vaporization for water is approximately 40.7 kJ/mol (or 40.7 J/g).
Converting grams to moles:
51g / 18.02 g/mol = 2.827 mol
Calculating the enthalpy change:
ΔH = 2.827 mol * 40.7 kJ/mol = 115.093 kJ (or 115,093 J)
Now we can substitute the values into the formula to find the entropy change:
ΔS = (51 g) * (115,093 J) / (373.15 K) = 15.69 J/K
Therefore, the entropy change when 51g of steam condenses to water at 100 °C is 15.69 J/K.