Question

A common chemistry demonstration is to dissolve ammonium nitrate into water. In a particular demonstration, 8.53 grams of ammonium nitrate were dissolved in 100.00 mL of water. As a result, the temperature of the solution dropped from 25.0 oC to 19.0 oC. Calculate q of the solution in Joules (assume m to be the total mass of solution).

Answer 1

Assume the density of water to be 1.0 g/mL at 25°C; the mass of 100.0 mL of water = (100.0 mL)*(1.0 g/mL) = 100.0 g.

Total mass of solution = (mass of ammonium nitrate) + (mass of water) = (8.53 g) + (100.0 g) = 108.53 g.

Change in temperature of the solution = (25°C) – (19°C) = 6°C.

Since the solution contains mostly water, we can assume the specific heat capacity of the solution to be equal to the specific heat capacity of the solution, i.e, 4.18 J/g.°C.

q_solution = (mass of solution)*(specific heat capacity of solution)*(change in temperature) = (108.53 g)*(4.18 J/g.°C)*(6°C) = 2721.9324 J ≈ 2721.93 J (ans).