All Reaction Most Balance for Mass and Charge

University:
High School
Course:
High School Chemistry
Academic year:

2022
Views:

299

Pages:

5
Author:

Leslie Williamson

All ½ reactions MUST balance for MASS AND CHARGE Writing & Balancing Half-reactions: Every redox reaction consists of two parts: OXID and RED. A separate redox reaction showing the loss or gain of Electrons can be written for each of these half-reactions. Example #1: Mg + Cr³⁺ → Mg²⁺ + Cr Label oxidation #'s e- after Oxidation reaction arrow Mg → Mg²⁺ + 2e⁻ e- before Reduction reaction arrow Cr³⁺ + 3e⁻ → Cr e-s lost must always EQUAL e-s gained Add half-reactions together and cancel out electrons 3Mg → 3Mg²⁺ + 6e⁻ x2 6e⁻ + 2Cr³⁺ → 2Cr 3Mg + 2Cr³⁺ → 3Mg²⁺ + 2Cr Balanced for Mass & Charge Check overall reaction to make sure mass (# of Atoms) and charge (# of e⁻) are both balanced Example #2: Mg + Cl₂ → MgCl₂ Ox: Mg → Mg²⁺ + 2e⁻ Red: Cl₂ + 2e⁻ → 2Cl⁻ Example #3: Cu + 2AgNO₃ → 2Ag + Cu(NO₃)₂ Ox: Cu → Cu²⁺ + 2e⁻ Red: Ag⁺ + 1e⁻ → Ag x2 Practice: balance the following equations for both mass and charge using half-reactions Sn²⁺ + 2Fe³⁺ → Sn⁴⁺ + 2Fe²⁺ Ox: Sn²⁺ → Sn⁴⁺ + 2e⁻ Red: Fe³⁺ + e⁻ → Fe²⁺ x2 2Al + 3Fe²⁺ → 2Al³⁺ + 3Fe Ox: Al → Al³⁺ + 3e⁻ x2 Red: Fe²⁺ + 2e⁻ → Fe x3 Zn + Mg²⁺ → Zn²⁺ + Mg Ox: Zn → Zn²⁺ + 2e⁻ Red: Mg²⁺ + 2e⁻ → Mg Sn²⁺ + 2Ag⁺ → Sn⁴⁺ + 2Ag Ox: Sn²⁺ → Sn⁴⁺ + 2e⁻ Red: Ag⁺ + 1e⁻ → Ag x2 2Mn⁷⁺ + 10Cl⁻ → 2Mn²⁺ + 5Cl₂ Ox: Mn⁷⁺ + 5e⁻ → Mn²⁺ x2 Red: 2Cl⁻ → Cl₂ + 2e⁻ x5 H₂S + 4H₂O → S + 4H₃O⁺ Ox: S²⁻ → S + 2e⁻ x2 Red: 4H⁺ + 4e⁻ → 2H₂O KIO₃ + 3H₂SO₃ → KI + 3H₂SO₄ Ox: I⁵⁺ + 6e⁻ → I⁻ x3 Red: S⁴⁺ → S⁶⁺ + 2e⁻ x3 Cr₂O₇²⁻ + 3Pb²⁺ → 2Cr³⁺ + 3Pb⁴⁺ Ox: Cr₂O₇²⁻ + 14H⁺ + 6e⁻ → 2Cr³⁺ + 7H₂O Red: Pb²⁺ → Pb⁴⁺ + 2e⁻ x3 H₂ + F₂ → 2HF Ox: H₂ → 2H⁺ + 2e⁻ Red: F₂ + 2e⁻ → 2F⁻ 2Li + H₂ → 2LiH Ox: Li → Li⁺ + 1e⁻ x2 Red: H₂ + 2e⁻ → 2H⁻ 1. Given the unbalanced equation: [Fe^{3+} + Sn^{2+} \rightarrow Fe^{2+} + Sn^{4+}] When the reaction is completely balanced using the smallest whole numbers, the coefficient of Fe³⁺ will be 1 2 3 4 2. Given the unbalanced equation: [Fe + Ag^{+} \rightarrow Fe^{3+} + Ag] When the equation is correctly balanced using smallest whole numbers, the coefficient of Ag⁺ is 5 2 3 4 3. Given the unbalanced equation: [Br_{2} + 2e^{-} \rightarrow 2Br^{-}] [Sn^{0} \rightarrow Sn^{2+} + 2e^{-}] When the equation is correctly balanced using the smallest whole-number coefficients, the coefficient of Br₂ is 1 2 3 4 4. Given the unbalanced equation: [3Mg(s) + 2Fe^{3+} \rightarrow 3Mg^{2+} + 2Fe(s)] When the equation is completely balanced using smallest whole numbers, the coefficient of Mg(s) will be 1 2 3 4 5. When the redox equation Hg + 2Ag⁺ → Hg²⁺ + 2Ag is correctly balanced using smallest whole numbers, the coefficient in front of the Ag⁺ will be 5 2 3 4 6. When the redox equation 2Cr³⁺(aq) + 3Mn(s) → 2Cr(s) + 3Mn²⁺(aq) is completely balanced, the coefficient of Cr³⁺(aq) will be 1 2 3 4 7. Which redox equation is correctly balanced? Mg + H₂O → Mg²⁺ + H₂ Sn²⁺ + H₂ → Sn + 2H⁺ Cr³⁺ + Mg → Cr + Mg²⁺ Al³⁺ + K → Al + K⁺ 8. Which equation is correctly balanced? Ca + Mg²⁺ → Ca²⁺ + Mg Zn + Ag⁺ → Zn²⁺ + 4g Cu + Au³⁺ → Cu²⁺ + Au Al + Sn²⁺ → Al³⁺ + Sn 9. Given the unbalanced equation which represents aluminum metal reacting with an acid: [Al + H⁺ → Al³⁺ + H₂] What is the total number of moles of electrons lost by 1 mole of aluminum? 6 2 3 1