0.70 moles of an unknown solid is placed into water to make 150.0 mL of solution. The solution's temperature decreases by 8.4°C. Calculate ∆H for the dissolution of the unknown solid. (The specific heat of the solution is 4.18 J/g･°C and the density of the solution is 1.02 g/mL).

Explanation:

1. Mass of solution

2. Calorimetry

There are two energy flows in this reaction.

q₁ = heat from reaction

q₂ = heat to warm the water

The heat of solution is positive, because the water cooled down when the substance dissolved,

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