Balancing Redox Reactions: Acidic Solutions: Study with Video Lessons, Practice Problems & Examples

A 0.350 g sample of a certain semimetal M heated in air yielded the matching oxide M₂O₃. The reaction needed 7.67 mL of 0.125 M  Cr₂O₇²⁻  when the oxide was dissolved in aqueous acid and titrated with K₂Cr₂O₇. The unbalanced equation for the titration is H₃MO₃(aq) + Cr₂O₇²⁻(aq) → H₃MO₄(aq) + Cr³⁺(aq) (in acid).

How many moles of semimetal were present in the initial 0.350 g sample and how many moles of oxide were formed?

Rusting of steel can be prevented by coating it with aluminum. Provide the balanced reaction equation for the corrosion that happens (a) when aluminum is present and (b) when aluminum is not present.

A sample contains palladium, cadmium, and other impurities. The mass percent of palladium and cadmium can be determined using a process that starts with the sample being dissolved in hot nitric acid. Aqueous ammonia is used to lessen the acidity of the resulting solution of Cu²⁺ and Pd²⁺ ions, and then sodium thiocyanate (NaSCN) and sulfuric acid (H₂SO₄) are added to precipitate palladium thiocyanate (PdSCN). The collected solid PdSCN is dissolved in water, treated with potassium iodate (KIO₃) to produce iodine, and then titrated with aqueous sodium thiosulfate (Na₂S₂O₃). After PdSCN is removed, the filtrate is neutralized by adding aqueous ammonia. Then, a solution of diammonium hydrogen phosphate ((NH₄)₂HPO₄) is added, resulting in a precipitate of cadmium ammonium phosphate (CdNH₄PO₄). The precipitate is transformed into cadmium pyrophosphate (Cd₂P₂O₇) by heating it to 900 °C, which is then weighed. The equations involved in the process are: 

(1) Pd(s) + NO₃^—(aq) → Pd⁴⁺(aq) + NO(g) (in acid)

(2) Pd⁴⁺(aq) + SCN^—(aq) + HSO₃^—(aq) → Pd(SCN)₂(s) + HSO₄^—(aq) (in acid)

(3) Pd²⁺(aq) + IO₃^—(aq) → Pd⁴⁺(aq) + I₂(aq) (in acid)

(4) I₂(aq) + S₂O₃^2—(aq) → I^—(aq) + S₄O₆^2—(aq) (in acid)

(5) CdNH₄PO₄(s) → Cd₂P₂O₇(s) + H₂O(g) + NH₃(g)

Give the balance equation for each reaction.

Choose the half-reaction that is correctly classified as an oxidation or reduction from the list below:

Bromine liquid can be created in the laboratory by reacting KBr and MnO₂ with a strong acid. If Mn²⁺ is the reduction product, what is the balanced equation for the reaction?

25.0 mL of 0.275 M NaBrO₃ is added to a 150.0 mL solution containing 0.175 M KBr and 0.450 M HClO₃. The bromate and bromide ions react to produce bromine liquid. After the reaction, what are the concentrations of all the ions in the solution? Make sure the solution is electrically neutral by checking your concentrations.

For a galvanic cell, the anode half-cell is Ni/Ni²⁺ and the cathode half-cell is F₂/F⁻. What are the balanced electrode equations and the balanced overall cell reaction?

What are the unbalanced reduction and oxidation half-reactions for Mn²⁺(aq) + ClO₂(g)  → MnO₂(s) + ClO₂⁻(aq)?

Is the following half-reaction a reduction or an oxidation? 

Is the following half-reaction a reduction or an oxidation? 

A 0.175 g sample of a specific semimetal M heated in air yielded the corresponding oxide MO₂. The reaction required 17.50 mL of 0.550 M MnO₄⁻ when the oxide was dissolved in aqueous acid and titrated with KMnO₄. 

H₂MO₃(aq) + MnO₄⁻(aq) → Mn²⁺(aq) + H₂MO₄(aq) (unbalanced)

Give the name of the semimetal M.

A bronze sample was subjected to preceding analysis. The reactions involved have the following unbalanced equations:

Sn²⁺(aq) + IO₃⁻(aq) → I₂(aq) + Sn⁴⁺(aq)

If 3.6218 g of sample needs 11.26 mL of 0.1300 M Na₂S₂O₃, what is the mass percent of tin in the sample?

The Winkler method can be used to determine the amount of dissolved oxygen in water samples by converting dissolved oxygen to MnO₂ with MnSO₄ and reacting it with NaOH and KI. The solution is then acidified for the oxidation of I⁻ to I₃⁻ by MnO₂ to occur. The amount of I₃⁻ formed is determined by titration with S₂O₃²⁻. The unbalanced equations are

Mn²⁺(aq) + O₂(g)→ MnO₂(s)

MnO₂(s)+ I⁻(aq) →Mn2+(aq) + I₃⁻(aq)

When 0.1578 g of a water sample is analyzed, the reaction needs 17.55 mL of 0.1300 M Na₂S₂O₃. Calculate the mass percent of oxygen in the sample.

At 25 °C, the standard reduction potentials for the following reactions are 

H₂SO₃(aq) + 4 H⁺(aq) + 4 e⁻ → S(s) + 3 H₂O(l) E° = 0.45 V

2 HClO(aq) + 4 H⁺(aq) + 4 e⁻ → Cl₂(g) + 2 H₂O(l) E° = 1.61 V

In acidic solution, what is the balanced equation for the reaction between HClO(aq) and elemental S(s) that produces H₂SO₃(aq) and Cl₂(g)?

In an acidic solution, what is the balanced net ionic equation for the following reaction?

Give the balanced equation for the following half-reactions occurring in an acidic solution.

In an acidic solution, what is the coefficient on Co³⁺(aq) when the reaction is balanced?

Co³⁺(aq) + Mn²⁺(aq) → Co²⁺(aq) + MnO₄⁻(aq)

50.0 mL of 0.121 M KMnO₄ is added to a 50.0 mL solution containing 0.183 M MnCl₂ and 0.152 M HClO₃. The permanganate and manganese(II) ions react to produce manganese(IV) oxide. For the reaction, what is the balanced net ionic equation?

When the same substance is oxidized and reduced in an oxidation reaction, it is referred to as a disproportionation reaction. Complete and balance the following disproportionation reaction in an acidic solution: S₂O₄^2–(aq) → S₂O₃^2–(aq) + HSO₃^–(aq).

Write the balanced half-reactions under acidic conditions and identify whether it is an oxidation or a reduction reaction

BrO₃^-(aq) → Br₂(l) 

Write the balanced half-reactions under acidic conditions and identify whether it is an oxidation or a reduction reaction

PtCl₄^2-(aq) → Pt(s) + Cl^-(aq)

Identify the balanced redox reaction for the oxidation of Sn²⁺under acidic conditions by IO₄^- , NO₃^-,and MnO₄^- 

Balance the following redox reaction under acidic conditions and identify the oxidizing and reducing agents:

Cr₂O₇^2- + U⁴⁺ → Cr³⁺ + UO₂²⁺

Balance the following redox reaction under acidic conditions and identify the oxidizing and reducing agents:

Bi(OH)₃+ SnO₂^2- → SnO₃^2- + Bi

Balance the following redox reaction under acidic conditions and identify the oxidizing and reducing agents:

HAuCl₄ + N₂H₄ → Au + N₂ + HCl

What is the balanced equation for the following redox reaction? 

Cr(s) + NO₃^-(aq) → NO(g) + Cr³⁺(aq)

How much 0.384 M NaNO₃ solution in mL is needed to thoroughly react with 4.23 g of Cr?

For the following redox reaction, balance under acidic conditions:

BrO₃^–(aq) + Sn²⁺(aq) → Sn⁴⁺(aq) + Br₂(l)

For the following redox reaction, balance under acidic conditions:

Ba(s) + Fe³⁺(aq) → Ba²⁺(aq) + Fe(s)

For the following redox reaction, balance under acidic conditions:

Na(s) + Fe³⁺(aq) → Fe(s) + Na⁺(aq)

Ozone reacts with hydrogen sulfide to form oxygen gas and sulfur. Balance this redox reaction in acidic condition.

Balance the following redox reaction in an acidic condition

PbO₂(s) + Cl^-(aq) → Pb²⁺(aq) + Cl₂(g)

Balance the following redox reaction in an acidic condition

MnO₄^-  + I^- → Mn²⁺ + I₂ 

Using the unbalanced half-reactions below, write the balanced overall reaction

a) Bi → Bi³⁺

b) Pa⁴⁺ → Pa

Balance the redox reaction in acidic conditions: 

TcO₄^- + HNO₂ → NO₃^- + Tc²⁺

i) Identify which species are oxidized and which are reduced. 

ii) Identify the oxidizing agent and reducing agent. 

Balance the following redox reaction and identify the number of electrons transferred.

Ca (s) + Al ³⁺(aq) → Al (s) + Ca ²⁺(aq)

Identify reduction half-reaction and oxidation half-reaction for the following:

CoO₂(s) + Br₂(l) → Co³⁺(aq) + HBrO(aq)

Balance the following reaction of 1.5 M dichromate: Cr₂O₇ ^2– →  Cr³⁺ in acidic solution. 

What is the coefficient on water in the balanced equation?

Balance the following redox reaction in acidic solution.

HNO₃ + H₂S → NO + S + H₂O

Complete and balance the equation for the reaction in acidic solution: CdS + NO₃^- → Cd²⁺ + S + NO

1. Identify oxidizing agent:

2. Identify reducing agent:

3. Identify element that is oxidized:

4. Identify element that is reduced: