Question

How much solution could be heated to boiling by the heat evolved by the dissolution of 24.0 g of naoh? (for the solution, assume a heat capacity of 4.0 j/g⋅∘c, an initial temperature of 25.0 ∘c, a boiling point of 100.0 ∘c, and a density of 1.05 g/ml.)?

Answer 1

Sodium hydroxide (NaOH) has a lattice energy of -887 kJ/mol and a heat of hydration of -932 kJ/mol.
Heat of dissolution of 1 mol of NaOH is 887 kJ/mol - 932 kJ/mol = -45 kJ/mol.
m(NaOH) = 24 g.
n(NaOH) = 24 g ÷ 40g/mol = 0,6 mol.
ΔT = 100°C - 25°C = 75°C.
Heat of dissolution of 0,6 mol of NaOH is -45 kJ/mol · 0,6 mol = -27 kJ.
27000 J = m · 4 J/g·°C · 75°C.
m(NaOH) = 90 g of solution.
d = m÷V, V = 90 g ÷ 1,05 g/ml = 85,7 ml.