Question

Complete and balance the equations for the following single-displacement reactions: a. \(\mathrm{Zn}+\mathrm{Pb}\left(\mathrm{NO}_{3}\right)_{2} \longrightarrow\) ________ b. \(\mathrm{Al}+\mathrm{Hg}\left(\mathrm{CH}_{3} \mathrm{COO}\right)_{2} \longrightarrow\) ________ c. \(\mathrm{Al}+\mathrm{NiSO}_{4} \longrightarrow\) ________ d. \(\mathrm{Na}+\mathrm{H}_{2} \mathrm{O} \longrightarrow\) ________

Short answer

a. \(\text{Zn} + \text{Pb(NO}_3\text{)}_2 \rightarrow \text{Zn}(\text{NO}_3\text{)}_2 + \text{Pb}\). b. \(\text{2Al} + 3\text{Hg(CH}_3\text{COO)}_2 \rightarrow 2\text{Al}(\text{CH}_3\text{COO)}_3 + 3\text{Hg}\). c. \(\text{2Al} + 3\text{NiSO}_4 \rightarrow \text{Al}_2(\text{SO}_4)_3 + 3\text{Ni}\). d. \(\text{2Na} + 2\text{H}_2\text{O} \rightarrow 2\text{NaOH} + \text{H}_2\)

Step-by-step solution

Identify the type of reaction

These are single-displacement reactions, where one element displaces another in a compound.

Predict the products

For single-displacement reactions, the more reactive element replaces the less reactive element in the compound.

Balance the reaction

Make sure the number of atoms for each element is equal on both sides of the equation.

Sub-step 3a: Reaction a

Starting with \(\text{Zn} + \text{Pb(NO}_3\text{)}_2 \rightarrow \text{Zn}(\text{NO}_3\text{)}_2 + \text{Pb}\), Zinc displaces Lead: Balanced reaction: \(\text{Zn} + \text{Pb(NO}_3\text{)}_2 \rightarrow \text{Zn}(\text{NO}_3\text{)}_2 + \text{Pb}\)

Sub-step 3b: Reaction b

Starting with \(\text{Al} + \text{Hg(CH}_3\text{COO)}_2 \rightarrow \text{Al}(CH}_3\text{COO}_2 + \text{Hg}\), Aluminum displaces Mercury: Balanced reaction: \(\text{2Al} + 3\text{Hg(CH}_3\text{COO)}_2 \rightarrow 2Al(\text{CH}_3\text{COO)}_3 + 3\text{Hg}\)

Sub-step 3c: Reaction c

Starting with \(\text{Al} + \text{NiSO}_4 \rightarrow \text{Al}_2(\text{SO}_4)_3 + \text{Ni}\), Aluminum displaces Nickel: Balanced reaction: \(\text{2Al} + 3\text{NiSO}_4 \rightarrow \text{Al}_2(\text{SO}_4)_3 + 3\text{Ni}\)

Sub-step 3d: Reaction d

Starting with \(\text{Na} + \text{H}_2\text{O} \rightarrow \text{NaOH} + \text{H}_2\), Sodium displaces Hydrogen: Balanced reaction: \(\text{2Na} + 2\text{H}_2\text{O} \rightarrow 2\text{NaOH} + \text{H}_2\)

Key concepts

Single-displacement reactions

In single-displacement reactions, one element in a compound is replaced by another element. These reactions are also called single replacement reactions. For instance, the reaction \(\text{Zn} + \text{Pb(NO}_3\text{)}_2 \rightarrow \text{Zn}(\text{NO}_3\text{)}_2 + \text{Pb}\) illustrates Zinc displacing Lead. Understanding which element will replace another is key to predicting products.
Single-displacement reactions often involve metals replacing metals or halogens replacing halogens. These reactions are guided by the reactivity series, which lists elements in order of reactivity. A more reactive element will replace a less reactive element in a compound.

Chemical reactivity

Chemical reactivity refers to the tendency of a substance to engage in chemical reactions. Elements in the reactivity series can be ranked by how easily they lose or gain electrons. For example, in the reaction \(\text{2Al} + 3\text{NiSO}_4 \rightarrow \text{Al}_2(\text{SO}_4)_3 + 3\text{Ni}\), Aluminum replaces Nickel because Aluminum is more reactive.
The reactivity series of metals is a helpful tool. It predicts the products of single-displacement reactions. The series goes from highly reactive metals, like Potassium and Sodium, to less reactive ones like Gold and Silver. Using the reactivity series ensures we correctly predict and balance reactions.

Stoichiometry

Stoichiometry is the study of the quantitative relationships in chemical reactions. It helps us balance chemical equations by ensuring the same number of atoms for each element on both sides of the reaction. For a balanced equation, the law of conservation of mass must be obeyed.
For example, in the reaction: \(\text{2Na} + 2\text{H}_2\text{O} \rightarrow 2\text{NaOH} + \text{H}_2\), we balance Sodium and Hydrogen atoms to ensure both sides have equal atom counts. The balanced equation shows that 2 moles of Sodium react with 2 moles of Water to produce 2 moles of Sodium Hydroxide and 1 mole of Hydrogen gas.

Reaction balancing

Balancing chemical reactions is crucial to accurately represent chemical processes. The aim is to ensure that the number of atoms for each element is the same on both sides of the equation. This means following these steps:

• Write the unbalanced equation first.
• Count the number of atoms for each element in the reactants and products.
• Add coefficients to balance the atoms, starting with the most complex molecule.
• Check your work to ensure atom counts are equal on both sides.

Taking the reaction \(\text{2Al} + 3\text{Hg(CH}_3\text{COO)}_2 \rightarrow 2\text{Al(CH}_3\text{COO)}_3 + 3\text{Hg}\), we start by counting atoms, then adjusting coefficients to balance the equation.