Question

Write balanced molecular and net ionic equations for the reactions of (a) hydrochloric acid with nickel, (b) dilute sulfuric acid with iron, (c) hydrobromic acid with magnesium, (d) acetic acid, \(\mathrm{CH}_{3} \mathrm{COOH},\) with zinc.

Short answer

The short answers for the net ionic equations are: (a) \(2H⁺(aq) + Ni(s) \rightarrow Ni⁺²(aq) + H₂(g)\) (b) \(2H⁺(aq) + Fe(s) \rightarrow Fe⁺²(aq) + H₂(g)\) (c) \(Mg(s) + 2H⁺(aq) \rightarrow Mg⁺²(aq) + H₂(g)\) (d) \(Zn(s) + 2H⁺(aq) \rightarrow Zn⁺²(aq) + H₂(g)\)

Step-by-step solution

Write reactants and possible products

Ni(s) + HCl(aq) -> NiCl₂(aq) + H₂(g)

Balance the molecular equation

2HCl(aq) + Ni(s) -> NiCl₂(aq) + H₂(g)

Write the complete ionic equation

2H⁺(aq) + 2Cl⁻(aq) + Ni(s) -> Ni⁺²(aq) + 2Cl⁻(aq) + H₂(g)

Write the net ionic equation

2H⁺(aq) + Ni(s) -> Ni⁺²(aq) + H₂(g) #b# Dilute sulfuric acid with iron

Write reactants and possible products

Fe(s) + H₂SO₄(aq) -> FeSO₄(aq) + H₂(g)

Balance the molecular equation

H₂SO₄(aq) + Fe(s) -> FeSO₄(aq) + H₂(g)

Write the complete ionic equation

2H⁺(aq) + SO₄⁻²(aq) + Fe(s) -> Fe⁺²(aq) + SO₄⁻²(aq) + H₂(g)

Write the net ionic equation

2H⁺(aq) + Fe(s) -> Fe⁺²(aq) + H₂(g) #c# Hydrobromic acid with magnesium

Write reactants and possible products

Mg(s) + HBr(aq) -> MgBr₂(aq) + H₂(g)

Balance the molecular equation

Mg(s) + 2HBr(aq) -> MgBr₂(aq) + H₂(g)

Write the complete ionic equation

Mg(s) + 2H⁺(aq) + 2Br⁻(aq) -> Mg⁺²(aq) + 2Br⁻(aq) + H₂(g)

Write the net ionic equation

Mg(s) + 2H⁺(aq) -> Mg⁺²(aq) + H₂(g) #d# Acetic acid with zinc

Write reactants and possible products

Zn(s) + CH₃COOH(aq) -> Zn(CH₃COO)₂(aq) + H₂(g)

Balance the molecular equation

Zn(s) + 2CH₃COOH(aq) -> Zn(CH₃COO)₂(aq) + H₂(g)

Write the complete ionic equation

Zn(s) + 2CH₃COO⁻(aq) + 2H⁺(aq) -> Zn⁺²(aq) + 2CH₃COO⁻(aq) + H₂(g)

Write the net ionic equation

Zn(s) + 2H⁺(aq) -> Zn⁺²(aq) + H₂(g)

Key concepts

Balanced Chemical Equations

Balanced chemical equations are foundational to understanding chemical reactions. They express the principle of conservation of mass — that atoms are neither created nor destroyed during a chemical reaction. To obtain a balanced equation, one must ensure that the count of each type of atom on the reactant side equals the count on the product side.

• For example, consider the reaction of hydrochloric acid with nickel: the equation is balanced by writing 2HCl(aq) + Ni(s) -> NiCl2(aq) + H2(g), which shows that there are equal numbers of hydrogen, chlorine, and nickel atoms on both sides of the reaction.

It's essential for students to practice balancing chemical equations as it is a critical skill in chemistry that applies to further concepts such as stoichiometry and net ionic equations.

Molecular Equations

Molecular equations provide a clearer picture of the chemicals involved in a reaction. They are written using the chemical formulas of the compounds in their standard states. These equations, typically used for double displacement reactions in aqueous solutions, describe the reactants and products completely without indicating the ionic character.

• For instance, when dilute sulfuric acid reacts with iron, the molecular equation is H2SO4(aq) + Fe(s) -> FeSO4(aq) + H2(g).

This is a stepping stone to writing complete ionic and net ionic equations and plays a significant role in visualizing chemical reactions in their entirety.

Acid-Metal Reactions

Acid-metal reactions are a type of single displacement reaction where a metal displaces hydrogen from an acid, forming a salt and hydrogen gas.

• The activity series of metals can predict if a reaction will occur. More active metals like magnesium will react with hydrobromic acid, as reflected by the balanced chemical equation: Mg(s) + 2HBr(aq) -> MgBr2(aq) + H2(g) — this illustrates that magnesium is more active than hydrogen.

Understanding these reactions is crucial since they involve the release of hydrogen gas, which is flammable and requires proper handling.

Stoichiometry

Stoichiometry is a branch of chemistry that deals with the quantitative aspects of chemical reactions. It is based on the balanced chemical equations and allows chemists to calculate the amounts of reactants and products involved in a chemical reaction.

• In the reaction of acetic acid with zinc, the stoichiometry of the balanced molecular equation Zn(s) + 2CH3COOH(aq) -> Zn(CH3COO)2(aq) + H2(g) tells us that one mole of zinc reacts with two moles of acetic acid to produce one mole of zinc acetate and one mole of hydrogen gas.

Being adept at stoichiometry is essential for making predictions about the outcomes of reactions and for practical applications, such as calculating the amount of reactants needed to produce a desired amount of product in a chemical process.