Solid potassium hydroxide may be used to unclog sink drains. the dissolution of potassium hydroxide in water is quite exothermic. what are the signs of δhsys and qsurr?

Answer is: The sign of ΔHsys is - and the sign of qsurr is +.

First Law of Thermodynamics - any heat lost by the system must be absorbed by the surroundings.

-qsystem = qsurroundings.

There are two types of reaction:

1) exothermic reaction (chemical reaction that releases more energy than it absorbs).  

For example, ΔH(reaction) = -225 kJ/mol; this is exothermic reaction.

2) endothermic reaction (chemical reaction that absorbs more energy than it releases).

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