QuestionFor parts of the free-response question that require calculations, clearly show the method used and the steps involved in arriving at your answers. You must show your work to receive credit for your answer. Examples and equations may be included in your answers where appropriate. $\mathrm{Mg}(s)+2 \mathrm{HCl}(a q) \rightarrow \mathrm{MgCl}_{2}(a q)+\mathrm{H}_{2}(g)$
In an experiment, a student places a small piece of pure $\mathrm{Mg}(s)$ into a beaker containing $250 . \mathrm{mL}$ of 6.44 $M \mathrm{HCl}(\mathrm{aq})$ . A reaction occurs, as represented by the equation above. (a) Write the balanced net ionic equation for the reaction between $\mathrm{Mg}(s)$ and $\mathrm{HCl}(a q)$ .
Note On your AP Exam, you will handwrite your responses to free-response questions in a test booklet $\square$

Studdy Solution

STEP 1

1. The given chemical equation is a molecular equation.
2. We need to write the balanced net ionic equation for the reaction.
3. Only strong electrolytes, weak electrolytes, and insoluble substances are involved in the net ionic equation.
4. We assume that $\mathrm{HCl}$ is a strong acid and dissociates completely in water.

STEP 2

1. Write the complete ionic equation for the reaction.
2. Identify and cancel the spectator ions.
3. Write the balanced net ionic equation.

STEP 3

Write the complete ionic equation by dissociating all strong electrolytes into their respective ions.
The molecular equation is: $\mathrm{Mg}(s) + 2 \mathrm{HCl}(aq) \rightarrow \mathrm{MgCl}_{2}(aq) + \mathrm{H}_{2}(g)$
Dissociate the strong electrolytes: $\mathrm{Mg}(s) + 2 \mathrm{H}^{+}(aq) + 2 \mathrm{Cl}^{-}(aq) \rightarrow \mathrm{Mg}^{2+}(aq) + 2 \mathrm{Cl}^{-}(aq) + \mathrm{H}_{2}(g)$

STEP 4

Identify the spectator ions in the complete ionic equation. Spectator ions are ions that appear on both sides of the equation without undergoing any change.
In this case, the spectator ions are: $2 \mathrm{Cl}^{-}(aq)$
Cancel the spectator ions from both sides of the equation: $\mathrm{Mg}(s) + 2 \mathrm{H}^{+}(aq) \rightarrow \mathrm{Mg}^{2+}(aq) + \mathrm{H}_{2}(g)$

STEP 5

Write the balanced net ionic equation, which includes only the species that undergo a change during the reaction:
$\mathrm{Mg}(s) + 2 \mathrm{H}^{+}(aq) \rightarrow \mathrm{Mg}^{2+}(aq) + \mathrm{H}_{2}(g)$
This is the balanced net ionic equation for the reaction.

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