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harina [27]
3 years ago
5

Which of the following equations represents an exothermic reaction? (Select all that apply.)

Chemistry
2 answers:
frez [133]3 years ago
7 0

Answer:

CH₄ + 2O₂ ⟶ CO₂ + 2H₂O + 212 800 cal

Step-by-step explanation:

CH₄ + 2O₂ ⟶ CO₂ + 2H₂O + 212 800 cal  

The heat is on the right-hand side of the equation, so the reaction is releasing heat.

The reaction is <em>exothermic</em>.

A is <em>wrong</em>. Your sign of ΔH is wrong, because graphite is the more stable form of carbon. We must add energy to graphite to convert it to diamond, so the process is<em> endothermic</em>.

B and D are <em>wrong</em>, because a ΔH > 0 indicates an <em>endothermic</em> reaction.

Elza [17]3 years ago
3 0

Answer:

C (graphite) → C (diamond), ΔH = - 0.45 kcal

CH4 + 2O2 → CO2 + 2H2O + 212,800 cal

Explanation:

exothermic reactions are characterized by releasing heat to the surroundings; the enthalpy change is negative, and the system temperature increases.

NH3 (g) + 12.0 kcal → ½N2 (g) + 3/2 H2 (g): it is not exothermic.

C (graphite) → C (diamond), ΔH = - 0.45 kcal: the reaction is exothermic because ΔH is negative

C + 2S → CS2, ΔH = 27,550 cal: it is not exothermic because the enthalpy change is positive

CH4 + 2O2 → CO2 + 2H2O + 212,800 cal: it is exothermic because it releases heat.

2H2O → 2H2 + O2, ΔH = +58 kcal: it is not exothermic because ΔH is positive.

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