Question

Consider the following reactions. (Note: (s) = solid, (l) = liquid, and (g) = gas.)
Mg(s) + ½O2(g) → MgO(s) + 146 kcal/mole
H2(g) + ½O2(g) → H2O(g), ΔH = -57.82 kcal/mole
The temperature of the surroundings will:

increase
decrease

Answer 1

increase because the reaction is exothermic

Answer 2

Answer:

Increase

Explanation:

A reaction can be exothermic or endothermic. An exothermic reaction, the heat flows from the system, means the system is losing heat, so the temperature of the system decreases and the temperature of the surroundings increases.

In an endothermic reaction, the heat flows to the system, so it's gain heat, the temperature of the system increase and the temperature of the surroundings decreases.

The enthalpy (H) is a measure of this heat, so for an exothermic reaction, it must decrease (because the system loses heat) and the variation ΔH must be negative. For an endothermic reaction, the opposite must occurs.

Then the reaction given is exothermic, the system loses heat and the temperature of the surroundings increase.