The molar enthalpy of vaporization for water
is 40.79 kJ/mol. Express this enthalpy of
vaporization in joules per gram.
b. The molar enthalpy of fusion for water is
6.009 kJ/mol. Express this enthalpy of fusion
in joules per gram.
To express the enthalpy of vaporization and fusion in joules per gram, we need to convert the given values from kJ/mol to J/g.
a. Enthalpy of vaporization:
Given: Molar enthalpy of vaporization = 40.79 kJ/mol
To convert this to joules per gram, we need to know the molar mass of water. The molar mass of water (H2O) is approximately 18.015 g/mol.
The enthalpy of vaporization (ΔHvap) in joules per gram can be calculated using the following formula:
ΔHvap (J/g) = (ΔHvap in kJ/mol) / (Molar mass in g/mol)
ΔHvap (J/g) = 40.79 kJ/mol / 18.015 g/mol
ΔHvap (J/g) ≈ 2260 J/g
Therefore, the enthalpy of vaporization for water is approximately 2260 J/g.
b. Enthalpy of fusion:
Given: Molar enthalpy of fusion = 6.009 kJ/mol
To convert this to joules per gram, we again need to know the molar mass of water, which is 18.015 g/mol.
The enthalpy of fusion (ΔHfus) in joules per gram can be calculated as:
ΔHfus (J/g) = (ΔHfus in kJ/mol) / (Molar mass in g/mol)
ΔHfus (J/g) = 6.009 kJ/mol / 18.015 g/mol
ΔHfus (J/g) ≈ 333 J/g
Therefore, the enthalpy of fusion for water is approximately 333 J/g.
To express the enthalpy of vaporization and enthalpy of fusion in joules per gram, we need to convert from kJ/mol to J/g.
a. Enthalpy of Vaporization:
The molar enthalpy of vaporization for water is given as 40.79 kJ/mol.
To convert this to J/g, you will need to know the molar mass of water, which is approximately 18.02 g/mol.
The enthalpy of vaporization in J/g can be calculated using the following steps:
Step 1: Convert kJ to J.
40.79 kJ/mol = 40.79 × 10^3 J/mol
Step 2: Calculate the enthalpy of vaporization in J/g.
Divide the enthalpy of vaporization in J/mol by the molar mass of water in g/mol.
Enthalpy of vaporization in J/g = (40.79 × 10^3 J/mol) / (18.02 g/mol)
By performing the calculation, you will find that the enthalpy of vaporization for water is approximately 2266 J/g.
b. Enthalpy of Fusion:
The molar enthalpy of fusion for water is given as 6.009 kJ/mol.
To convert this to J/g, you will apply the same steps as before, using the molar mass of water.
Step 1: Convert kJ to J.
6.009 kJ/mol = 6.009 × 10^3 J/mol
Step 2: Calculate the enthalpy of fusion in J/g.
Divide the enthalpy of fusion in J/mol by the molar mass of water in g/mol.
Enthalpy of fusion in J/g = (6.009 × 10^3 J/mol) / (18.02 g/mol)
By performing the calculation, you will find that the enthalpy of fusion for water is approximately 333 J/g.
40.79 kJ/mol x (1000 J/kJ) x (1 mol H2O/18.015 g H2O) = ?
You do b in a similar fashion. It's simply a matter of making the dimensional factors work for you.