Question

2hcl + mg → mgcl₂ + h₂
calculate δh for the reaction.
qᵣₓₙ = -9240 j 0.0200 mol mg
δh = ? kj/mol
enter either a + or - sign and the magnitude.

Explanation:

Step1: Recall the relationship between \( q_{rxn} \) and \( \Delta H \)

The enthalpy change of a reaction (\( \Delta H \)) is the heat of the reaction per mole of the reactant (or product) involved. The formula is \( \Delta H=\frac{q_{rxn}}{n} \), where \( n \) is the number of moles of the substance (here, Mg) and \( q_{rxn} \) is the heat of the reaction. Also, we need to convert joules to kilojoules (since \( 1\space kJ = 1000\space J \)).

Step2: Substitute the values and convert units

Given \( q_{rxn}=- 9240\space J=-9240\div1000\space kJ=-9.24\space kJ \) (converting J to kJ) and \( n = 0.0200\space mol \) (moles of Mg).

Now, use the formula \( \Delta H=\frac{q_{rxn}}{n} \)

Substitute \( q_{rxn}=-9.24\space kJ \) and \( n = 0.0200\space mol \) into the formula:

\( \Delta H=\frac{- 9.24\space kJ}{0.0200\space mol}=-462\space kJ/mol \)

Answer:

\(-462\)