The burning of magnesium may be represented by:
`2Mg(s) +O_(2)(g) rarr 2MgO(s), DeltaH^(Theta) =- 1204 kJ (mol)^(-1)`
Which one of the following correctly describe what would happen if the reaction were allowed to proceed at constant external pressure in such a way that no energy transfer could taken place between the reaction mixture and its surroundings?

Options

A. No reaction could occur.
B. The tempertaure of the reaction mixture would increase.
C. The temperature of the reaction mixture would decrease.
D. The pressure of the system would increase.

Explanation

To solve the problem regarding the burning of magnesium and its thermodynamic implications, let's break down the process step by step.

### Step 1: Understand the Reaction
The reaction given is:
\[ 2Mg(s) + O_2(g) \rightarrow 2MgO(s) \]
The enthalpy change (\(\Delta H\)) for this reaction is \(-1204 \, \text{kJ/mol}\), indicating that it is an exothermic reaction. This means that energy is released when magnesium burns in oxygen.

**Hint:** Identify the type of reaction (exothermic or endothermic) based on the sign of \(\Delta H\).
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