How much heat is evolved when 1258 g of water condenses to a liquid at 100.°C?
see below
The molar mass of water is 18.0 g/mol. 1255 g H2O x (1 mol / 18.0 g) = 69.7 mol H2O 69.7 mol H2O x (- 40.7 kJ/mol) = - 2840 kJ The negative sign shows that heat is given off.
-12.66
To calculate the amount of heat evolved when water condenses, we need to use the heat of vaporization of water. The heat of vaporization of water is the amount of energy required to change one gram of water from a liquid state to a gaseous state at a given temperature.
The heat of vaporization of water at its boiling point (100°C) is 40.7 kJ/mol, or 2260 J/g.
First, we need to determine the number of moles of water in 1258 g. The molar mass of water (H2O) is approximately 18 g/mol.
Moles of water = mass of water / molar mass of water
Moles of water = 1258 g / 18 g/mol
Moles of water ≈ 69.89 mol
Now, we can calculate the heat evolved using the formula:
Heat evolved = moles of water * heat of vaporization
Heat evolved = 69.89 mol * 40.7 kJ/mol
Heat evolved ≈ 2849 kJ
Therefore, when 1258 g of water condenses to a liquid at 100°C, approximately 2849 kJ of heat is evolved.