4. The dissolution of barium hydroxide in water is an exothermic process. Which

Question

4. The dissolution of barium hydroxide in water is an exothermic process. Which of the following statements is correct?
A) Theenthalpyofsolidbariumhydroxidepluspurewaterislessthanthatofthesolution,at the same temperature.
B) The enthalpy of solid barium hydroxide plus pure water is greater than that of the solution, at the same temperature.
C) Theenthalpyofsolidbariumhydroxidepluspurewateristhesameasthatofthesolution, at the same temperature.
D) The temperature of the solution is lower than of the barium hydroxide and water before mixing.
E) When barium hydroxide dissolves in water, the system does work on the surroundings.

Explanation / Answer

The answer is B. The enthalpy ( heat content ) of the barium hydroxide and water is more than the enthalpy of the solution. The reason is because heat is lost in the exothermic reaction
Trust me I did a chemistry degree!

Guy below me has the right idea, but has used the wrong equation hence the answer is B and NOT A

Enthalpy is a measure of energy content really. How can the final solution have more energy content if heat has been lost during the reaction?

The equation below is wrong it should be:

Enthalpy products - Enthalpy reactants = delta H

See 3rd line of http://www.ausetute.com.au/enthchan.html

This is why the guy below has the opposite answer.


The simple way of looking at it is

Reactants have energy, they lose some during the reaction, this means the products will have even less energy content hence B!!

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