Problem: Which one of the following processes is endothermic?a. 2 H2 (g) + O2 (g) → 2 H2O (g)b. H2O (g) → H 2O (l)c. CH4 (g) + 2 O2 (g) → CO2 (g) + 2 H2O (g)d. H2O (s) → H2O (l)e. 2 Al (s) + Fe2O3 (s) → Al2O3 (s) + 2 Fe (s)

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FREE Expert Solution

We’re being asked to determine which of the following processes is endothermic.


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


Analyzing process given:

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Problem Details

Which one of the following processes is endothermic?

a. 2 H2 (g) + O(g) → 2 H2O (g)

b. H2O (g) → H 2O (l)

c. CH4 (g) + 2 O2 (g) → CO2 (g) + 2 H2O (g)

d. H2O (s) → H2O (l)

e. 2 Al (s) + Fe2O3 (s) → Al2O3 (s) + 2 Fe (s)

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