Question

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Answer 1

a) NaBr + Cl₂ → NaCl + Br₂

$\overset{+ 1}{N a} \overset{- 1}{B r} + {\overset{0}{C l}}_{2} \to \overset{+ 1}{N a} \overset{- 1}{C l} + {\overset{0}{B r}}_{2}$

$\begin{array}{l} \overset{- 1}{B r} \to {\overset{0}{B r}}_{} + 1 e \\ \overset{0}{C l} + 1 e \to \overset{- 1}{C l} \end{array}$

$\begin{matrix} 1 \times \\ 1 \times \end{matrix} |\begin{array}{l} \overset{- 1}{B r} \to {\overset{0}{B r}}_{} + 1 e \\ \overset{0}{C l} + 1 e \to \overset{- 1}{C l} \end{array}$

⇒ $\overset{- 1}{B r} + \overset{0}{C l} \to \overset{0}{B r} + \overset{- 1}{C l}$

2NaBr + Cl₂ → 2NaCl + Br₂

b) Fe₂O₃ + CO → Fe + CO₂

${\overset{+ 3}{F e}}_{2} {\overset{- 2}{O}}_{3} + \overset{+ 2}{C} \overset{- 2}{O} \to \overset{0}{F e} + \overset{+ 4}{C} {\overset{- 2}{O}}_{2}$

$\begin{array}{l} \overset{+ 3}{F e} + 3 e \to \overset{0}{F e} \\ \overset{+ 2}{C} \to \overset{+ 4}{C} + 2 e \end{array}$

$\begin{matrix} 2 \times \\ 3 \times \end{matrix} |\begin{array}{l} \overset{+ 3}{F e} + 3 e \to \overset{0}{F e} \\ \overset{+ 2}{C} \to \overset{+ 4}{C} + 2 e \end{array}$

⇒ $2 \overset{+ 3}{F e} + 3 \overset{+ 2}{C} \to 2 \overset{0}{F e} + 3 \overset{+ 4}{C}$

Fe₂O₃ + 3CO → 2Fe + 3CO₂

c) CO + I₂O₅ → CO₂ + I₂

$\overset{+ 2}{C} \overset{- 2}{O} + {\overset{+ 5}{I}}_{2} {\overset{- 2}{O}}_{5} \to \overset{+ 4}{C} {\overset{- 2}{O}}_{2} + {\overset{0}{I}}_{2}$

$\begin{array}{l} \overset{+ 2}{C} \to \overset{+ 4}{C} + 2 e \\ \overset{+ 5}{I} + 5 e \to \overset{0}{I} \end{array}$

$\begin{matrix} 5 \times \\ 2 \times \end{matrix} |\begin{array}{l} \overset{+ 2}{C} \to \overset{+ 4}{C} + 2 e \\ \overset{+ 5}{I} + 5 e \to \overset{0}{I} \end{array}$

⇒ $5 \overset{+ 2}{C} + 2 \overset{+ 5}{I} \to 5 \overset{+ 4}{C} + 2 \overset{0}{I}$

5CO + I₂O₅ → 5CO₂ + I₂

d) Cr(OH)₃ + Br₂ + OH^- → CrO₄^2- + Br^- + H₂O

$\begin{array}{l} \overset{0}{B r} + 1 e \to B r^{-} \\ C r {(O H)}_{3} + 5 O H^{-} \to C r {O_{4}}^{2 -} + 4 H_{2} O + 3 e \end{array}$

$\begin{matrix} 3 \times \\ 1 \times \end{matrix} |\begin{array}{l} \overset{0}{B r} + 1 e \to B r^{-} \\ C r {(O H)}_{3} + 5 O H^{-} \to C r {O_{4}}^{2 -} + 4 H_{2} O + 3 e \end{array}$

⇒ $C r {(O H)}_{3} + 3 B r + 5 O H^{-} \to C r {O_{4}}^{2 -} + 3 B r^{-} + 4 H_{2} O$

2Cr(OH)₃ + 3Br₂ + 10OH^- → 2CrO₄^2- + 6Br^- + 8H₂O

e) H⁺ + MnO₄^- + HCOOH → Mn²⁺ + H₂O + CO₂

$H^{+} + M n {O_{4}}^{-} + \overset{+ 1}{H} \overset{+ 2}{C} \overset{- 2}{O} \overset{- 2}{O} \overset{+ 1}{H} \to M n^{2 +} + H_{2} O + \overset{+ 4}{C} {\overset{- 2}{O}}_{2}$

$\begin{array}{l} \overset{+ 1}{H} \overset{+ 2}{C} \overset{- 2}{O} \overset{- 2}{O} \overset{+ 1}{H} \to \overset{+ 4}{C} {\overset{- 2}{O}}_{2} + 2 H^{+} + 2 e \\ 8 H^{+} + M n {O_{4}}^{-} + 5e \to M n^{2 +} + 4 H_{2} O \end{array}$

$\begin{matrix} 5 \times \\ 2 \times \end{matrix} |\begin{array}{l} \overset{+ 1}{H} \overset{+ 2}{C} \overset{- 2}{O} \overset{- 2}{O} \overset{+ 1}{H} \to \overset{+ 4}{C} {\overset{- 2}{O}}_{2} + 2 H^{+} + 2 e \\ 8 H^{+} + M n {O_{4}}^{-} + 5e \to M n^{2 +} + 4 H_{2} O \end{array}$

⇒ $16 H^{+} + 2 M n {O_{4}}^{-} + \overset{+ 1}{5 H} \overset{+ 2}{C} \overset{- 2}{O} \overset{- 2}{O} \overset{+ 1}{H} \to 2 M n^{2 +} + 8 H_{2} O + 5 \overset{+ 4}{C} {\overset{- 2}{O}}_{2} + 10 H^{+}$

6H⁺ + 2MnO₄^- + 5HCOOH → 2Mn²⁺ + 8H₂O + 5CO₂

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Answer 2