Question

1. What is the heat (q) needed by water with molar heat of vaporization of 40.7 kJ if it is 50.0 g in mass and boils at 100°C? Note that the molar mass of water is 18.0 g/mol.

2. How will you compare it with the heat needed by alcohol with molar heat of vaporization 44.0 kJ at 35.0 g and boils at 82.5°C? Note that the molar mass of isopropyl alcohol is 60.1 g/mol.

Answer 1

1. q = $\Delta H_{vap} ×$ $\frac{mass}{molar mass}$

q = 40.7 × $\frac{50}{18}$

q = 113.05 KJ

2. q = $\Delta H_{vap} ×$ $\frac{mass}{molar mass}$

q = 44 × $\frac{35}{60.1}$

q = 25.62 KJ