Balancing/Oxidation

Section 7.1 Overview

18. What is a chemical reaction?

• A chemical reaction can be defined as a process where one or more substances, known as reactants, are transformed into one or more different substances, known as products. This transformation involves the breaking of chemical bonds in the reactants and the formation of new chemical bonds to create the products.

a. Description of a Chemical Reaction

• In simple terms, a chemical reaction is a process that changes substances into different substances by breaking and forming chemical bonds. It indicates that the atoms in the reactant compounds reorganize to produce different products.

b. Examples of Chemical Reactions

1. Combustion of methane:

   • CH₄(g) + 2O₂(g) → CO₂(g) + 2H₂O(g)

2. Decomposition of water:

   • 2H₂O(l) → 2H₂(g) + O₂(g)

3. Synthesis of ammonia through the Haber process:

   • N₂(g) + 3H₂(g) → 2NH₃(g)

19. Conservation of Mass in Chemical Equations

• The law of conservation of mass states that mass is neither created nor destroyed in a chemical reaction. Therefore, the number of atoms before and after the reaction must be the same.

c. Equations that Conserve Mass:

1. N₂(g) + H₂(g) → NH₃(g)

   • This equation can be balanced as it conserves mass with 2 Nitrogen (N) and 6 Hydrogen (H) on both sides (1 N₂ + 3 H₂ yields 2 NH₃).

2. H₂(g) + Cl₂(g) → 2HCl(g)

   • This equation conserves mass by having 2 Hydrogen (H) and 2 Chlorine (Cl) atoms on both sides.

3. 2N₂H₄(g) + N₂O₄(g) → 2N₂(g) + 4H₂O(g)

   • Here, we have 2 Nitrogen from N₂H₄ and 2 from N₂O₄ which produces 2 N₂, and balances the mass with 4 Oxygen (O) atoms produced in 4 H₂O.

20. Balancing Equations and Predicting Products

a. Reactions to Balance and Predict:

1. Na + FeBr₃ →

   • Balanced: 3Na + FeBr₃ → 3NaBr + Fe

   • Products: Sodium bromide and Iron.

2. NaOH + H₂SO₄ →

   • Balanced: NaOH + H₂SO₄ → Na₂SO₄ + 2H₂O

   • Products: Sodium sulfate and water.

3. C₂H₄O₂ + O₂ →

   • Balanced: C₂H₄O₂ + 2O₂ → 2CO₂ + 2H₂O

   • Products: Carbon dioxide and water.

21. Solubility of Compounds

• Solubility rules help in predicting whether a compound is soluble in water or not. Referencing the Book Solubility Chart:

a. Solubility Status:

1. CUCO₃

   • Insoluble (Copper Carbonate is generally insoluble).

2. Na₃PO₄

   • Soluble (Sodium Phosphate is soluble).

3. Pb(NO₃)₂

   • Soluble (Lead(II) Nitrate is soluble).

4. K₂SO₄

   • Soluble (Potassium Sulfate is soluble).

5. MgSO₄

   • Soluble (Magnesium Sulfate is soluble).

Combustion, Fermentation, and Reactivity

23. Combustion of Propane (C₃H₈)

a. General Chemical Equation

• C₃H₈ + O₂ → CO₂ + H₂O

b. Balanced Chemical Equation

• C₃H₈ + 5O₂ → 3CO₂ + 4H₂O

24. Fermentation of Sugar

a. General Chemical Equation

• C₁₂H₂₂O₁₁ + H₂O → C₂H₅OH + CO₂

  • (Sugar reacts with water to produce ethyl alcohol and carbon dioxide)

b. Balanced Chemical Equation

• C₁₂H₂₂O₁₁ + 12H₂O → 12C₂H₅OH + 12CO₂

25. Reactivity of Potassium

a. General Chemical Equation

• K + H₂O → KOH(aq) + H₂(g)

b. Balanced Chemical Equation

• 2K + 2H₂O → 2KOH(aq) + H₂(g)

Reaction Types

26. Categorization of Chemical Reactions

• Classify the following reactions:

a. Combustion

• CH₄ + 2O₂ → 2H₂O + CO₂

b. Synthesis

• 2Ca(s) + O₂(g) → 2CaO(s)

c. Double replacement

• BaCl₂(aq) + Na₂SO₄(aq) → BaSO₄(s) + 2NaCl(aq)

d. Decomposition

• NH₄NO₃(aq) → N₂O(g) + 2H₂O(g)

e. Single replacement

• 2Fe(s) + 3Cl₂(g) → 2FeCl₃(aq)

27. Balancing and Classifying Chemical Reactions

a. Decomposition

• Ca(NO₃)₂ → CaO + N₂ + O₂

b. Decomposition

• NH₄Cl(s) → NH₃(g) + HCl(g)

c. Double replacement

• Na₂O(s) + H₂O → 2NaOH(aq)

d. Combustion

• C₆H₁₂O₆(S) + 6O₂(g) → 6CO₂(g) + 6H₂O(g)

28. Reaction Prediction and Classification

a. Predicting Products of NaBr + BaCl₂ →

• Products: BaBr₂ + NaCl

b. Balanced Equation

• 2NaBr + BaCl₂ → BaBr₂ + 2NaCl

c. Classification

• Double replacement reaction

29. Reaction Prediction and Classification

a. Predicting Products of C₆H₁₄ + O₂ →

• Products: CO₂ + H₂O

b. Balanced Equation

• 2C₆H₁₄ + 15O₂ → 12CO₂ + 14H₂O

c. Classification

• Combustion reaction

30. Additional Reaction Prediction

Given Cl₂ + KBr →

1. Predict Products: KCl + Br₂

2. Balanced Equation: Cl₂ + 2KBr → 2KCl + Br₂

3. Classification: Single replacement

Solubility Assessment

31. Solubility of Given Compounds

1. Potassium Nitrate (KNO₃)

• Soluble (Nitrates are generally soluble).

2. Calcium Carbonate (CaCO₃)

• Insoluble (Most carbonates are insoluble, except for alkali metal carbonates).

3. Ammonium Carbonate ((NH₄)₂CO₃)

• Soluble (Ammonium compound is soluble).

4. Silver Chloride (AgCl)

• Insoluble (Silver halides are generally insoluble).

5. Lithium Chloride (LiCl)

• Soluble (All lithium compounds are soluble).

32. Completing Balanced Reactions

Fill in the missing reactant or product:

1. — (to be determined for specific reaction)

2. 4NH₃ + 2H₂O + Ca(OH)₂ + H₂ → (Ca(NH₂)₂) + 2H₂

3. Fe₂O₃ + 2Al → (4Fe) + Al₂O₃

4. — (to be determined)

5. Ni + H₂ → NiCl₂ + H₂

Oxidation States

33. Oxidation Numbers in Compounds

a. Silicon Dioxide (SiO₂)

• Si: +4, O: -2

b. Bromine (Br₂)

• Br: 0

c. Potassium Chloride (KCl)

• K: +1, Cl: -1

d. Sodium Chloride (NaCl)

• Na: +1, Cl: -1

e. Nitrous Acid (HNO₂)

• H: +1, N: +3, O: -2

34. Finding Oxidation Numbers

a. Sulfur Dioxide (SO₂)

• S: +4, O: -2

b. Hydrogen Sulfide (H₂S)

• H: +1, S: -2

c. Sulfite Ion (SO₃²⁻)

• S: +4, O: -2

Redox Reactions

35. Identifying Oxidized and Reduced Elements

a. Reaction: 2NO(g) + 5H₂(g) → 2NH₃(g) + 2H₂O(g)

• Oxidized: N (from +2 to -3), Reduced: H (from 0 to +1)

• Oxidizing Agent: NO, Reducing Agent: H₂

b. Reaction: 2Na(s) + 2H₂O(l) → 2NaOH(aq) + H₂(g)

• Oxidized: Na (from 0 to +1), Reduced: H (from +1 to 0)

• Oxidizing Agent: H₂O, Reducing Agent: Na

c. Reaction: 2H₂O(l) → 2H₂(g) + O₂(g)

• Oxidized: O (from -2 to 0), Reduced: H (from +1 to 0)

• Oxidizing Agent: O₂, Reducing Agent: H₂O

d. Reaction: 4Li(s) + O₂(g) → 2Li₂O(s)

• Oxidized: Li (from 0 to +1), Reduced: O (from 0 to -2)

• Oxidizing Agent: O₂, Reducing Agent: Li