HC CHEMISTRY HC CHEMISTRY CHEMISTRY IN SOCIETY (C) CHEMICAL ENERGY.

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HC CHEMISTRY HC CHEMISTRY CHEMISTRY IN SOCIETY (C) CHEMICAL ENERGY

HC CHEMISTRY HC CHEMISTRY (C) CHEMICAL ENERGY Enthalpy of Solution

(B) CHEMISTRY IN SOCIETY HC CHEMISTRY HC CHEMISTRY (B) CHEMISTRY IN SOCIETY Enthalpy of solution After completing this lesson you should be able to : The enthalpy of solution of a substance is the enthalpy change when one mole of the substance dissolves in water. Carry out experiments to find enthalpies of solution.

Enthalpy of solution COPY The enthalpy of solution of a substance is the energy change when one mole of a substance dissolves in water. Higher Chemistry Eric Alan and John Harris

COPY Enthalpy of solution This is the energy change when 1 mole of solute dissolves in water The enthalpy of solution for NaOH can be represented by the equation NaOH(s) Na+(aq) + OH-(aq)

Measuring enthalpy of solution COPY Measuring enthalpy of solution Add 20ml water to 2 plastic beakers and take the temperature of both Accurately record the mass of approximately 2g of the 2 solids Add NaOH to one and record the final temperature reached Add ammonium nitrate to the other and record the final temperature mass (g) start temp ( oC) final temp change in temp sodium hydroxide ammonium nitrate

Measuring the enthalpy of solution COPY Measuring the enthalpy of solution The heat energy gained by the water (Eh) is calculated using the formula: Eh = c m ∆T Eh = x x = kJ

Measuring the enthalpy of solution COPY Measuring the enthalpy of solution The heat energy released on dissolving ……….. g of NaOH ………….. kJ So one mole .............. g of NaOH ...........kJ The enthalpy of solution of NaOH is -………….. kJ mol-1 (A negative sign is used because energy was released the temperature increased i.e. exothermic reaction)

Measuring the enthalpy of solution COPY Measuring the enthalpy of solution The heat energy released on dissolving ……….. g of NH4NO3 ……….. kJ So one mole .............. g of NH4NO3 ............kJ The enthalpy of solution of NH4NO3 is +………….. kJ mol-1 (A positive sign is used because energy was taken in the temperature decreased i.e. endothermic reaction)

Data book values NH4 NO3 +25.69kJ mol -1 NaOH -44.51 kJ mol -1 COPY Data book values NH4 NO3 +25.69kJ mol -1 NaOH -44.51 kJ mol -1 Comment on sources of inaccuracy

COPY ENTHALPIES OF SOLUTION AND HYDRATION Salt animation solution

COPY ENTHALPIES OF SOLUTION AND HYDRATION Salt animation solution

COPY Enthalpy of solution 14.76 kJ mol-1 The enthalpy of solution of a substance is the energy change when one mole of a substance dissolves in water. Worked example 1. 5g of ammonium chloride, NH4Cl, is completely dissolved in 100cm3 of water. The water temperature falls from 21oC to 17.7oC. Calculate the enthalpy of solution of ammonium chloride. 14.76 kJ mol-1 13

COPY Calculations for you to try. 1. 8g of ammonium nitrate, NH4NO3, is dissolved in 200cm3 of water. The temperature of the water falls from 20oC to 17.1oC. Calculate the enthalphy of solution. COPY 2. When 0.1 mol of a compound dissolves in 100cm3 of water the temperature of the water rises from 19oC to 22.4oC . Calculate the enthalpy of solution of the compound. 3. The enthalpy of solution of potassium chloride, KCl, is + 16.75kJ mol-1. What will be the temperature change when 14.9g of potassium chloride is dissolved in 150cm3 of water? 14

1. 8g of ammonium nitrate, NH4NO3, is dissolved in 200cm3 of water 1. 8g of ammonium nitrate, NH4NO3, is dissolved in 200cm3 of water. The temperature of the water falls from 20oC to 17.1oC. 24.2 kJ mol-1

2. When 0.1 mol of a compound dissolves in 100cm3 of water the temperature of the water rises from 19oC to 22.4oC . Calculate the enthalpy of solution of the compound. -14.2 kJ mol-1

3. The enthalpy of solution of potassium chloride, KCl, is + 16 3. The enthalpy of solution of potassium chloride, KCl, is + 16.75kJ mol-1. What will be the temperature change when 14.9g of potassium chloride is dissolved in 150cm3 of water? -5.34 oC 17