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Chemistry Physical question enthalpy of solution

A solution is formed when 5.00 g of potassium chloride are dissolved in 20.0 g of water. The initial temperature of the water is 298 K.

Why is the final temperature lower than 298K. I thought the reaction would be greater. How am I supposed to know if the reaction is endothermic or exothermic?
Original post by acabo1111
A solution is formed when 5.00 g of potassium chloride are dissolved in 20.0 g of water. The initial temperature of the water is 298 K.
Why is the final temperature lower than 298K. I thought the reaction would be greater. How am I supposed to know if the reaction is endothermic or exothermic?
You are not supposed to know. But if the temperature decreases then the process is endothermic.
Original post by acabo1111
A solution is formed when 5.00 g of potassium chloride are dissolved in 20.0 g of water. The initial temperature of the water is 298 K.
Why is the final temperature lower than 298K. I thought the reaction would be greater. How am I supposed to know if the reaction is endothermic or exothermic?
Hi, the temp decrease would show it is a endothermic reaction as energy is taken in to break the bonds between the KCl. Also once you work it out (this thred may help q=mcdeltaT A2 question - The Student Room) you will get a possitive result for the enthalpy change and this shows that it is a endothermic reaction too as the energy in the end is greater than the energy in the begging. So in other words the energy of the products is greater than the energy of the reactants. I hope this helps :smile: .

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