Question

The potassium thiocyanate is a clear colorless solution. Iron (III) nitrate is a very light yellow color. When these two solutions are combined, the color of the product is light red. When I added KSCN it turned a blood red color. In another test tube I put the potassium thiocyanate and iron nitrate in an ice bath for five minutes and the solution turned a darker color that it originally was. (Would this be a darker red - forgot to write down the color?). In another test tube with the potassium thiocyanate and iron nitrate, it was made warm to nearly boiling. Again, forgot to write down the color because we were running out of time. I believe the color was yellow and when it cooled it turned about to near its original color. Is this correct. My question is according to Le Chatelier principle is this an exothermic or endothermic reaction and why?

Answer 1

This is an exothermic reaction. This is because an exothermic reactions needs to generates heat to take place. It does not absorb energy or need heat to be done the reaction.

In this case, the reaction with these two compounds is spontaneus, and when it cools, means that is exerting heat to the surroundings. when it begins to absorbs heat (wheh you are heating) the reaction taking place is different, and when it cools, it turns to the original red, which is the product of the reaction with KSCN. So this is the exothermic reaction.