Question

In a coffee-cup calorimeter experiment, 10.00 g of a soluble ionic compound was added to the calorimeter containing 75.0 g H2O initially at 23.2°C. The temperature of the water increased to 31.8°C. What was the change in enthalpy for the dissolution of the compound? Give your answer in units of joules per gram of compound. Assume that the specific heat of the solution is the same as that of pure water, 4.18 J ⁄ (g ⋅ °C).

Answer 1

In chemistry, the point of view is the system, not the surroundings. The system in this case is the chemical and its dissolving. The surroundings would be the water which absorbs the heat. Since this reaction is exothermic, the proper sign in chemistry would be negative.

q =You know have 85 g of solution * 4.18 J/gC * (31.8C - 23.2C) = 3055 J. As energy is given offl the sign should be negative.

Since you had 10 g of the original solid, the result is -305.5 J/g or -3.1 * 10^2 J/g