Chemistry Practice Problems Endothermic & Exothermic Reactions Practice Problems Solution: If an endothermic reaction absorbs heat, then why ...

Solution: If an endothermic reaction absorbs heat, then why does it feel cold to the touch?

Problem

If an endothermic reaction absorbs heat, then why does it feel cold to the touch?

Solution

We’re being asked to explain why an endothermic reaction feels cold.


Recall that:

Exothermic reactions

lose energy, releases heat, temperature of the surroundings increases
▪ involves bond formation (for phase change: gas → liquid → solid)
ΔH is negative

Endothermic reactions

gain/requires energy, absorbs heat, temperature of the surroundings decreases
▪ involves breaking bonds (for phase change: solid → liquid → gas)
ΔH is positive


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Solved • Wed Oct 31 2018 12:47:06 GMT-0400 (EDT)

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Q. Consider the following reaction:2Mg(s) + O2 (g) → 2MgO(s)  ΔH = - 1204 kJIs this reaction exothermic or endothermic?

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