Problem 21 - Chemistry: The Central Science

Question

Balance the following equations and indicate whether they are combination, decomposition, or combustion reactions: (a) \(\mathrm{C}_{3} \mathrm{H}_{6}(g)+\mathrm{O}_{2}(g) \longrightarrow \mathrm{CO}_{2}(g)+\mathrm{H}_{2} \mathrm{O}(g)\) (b) \(\mathrm{NH}_{4} \mathrm{NO}_{3}(s) \longrightarrow \mathrm{N}_{2} \mathrm{O}(g)+\mathrm{H}_{2} \mathrm{O}(g)\) (c) \(\mathrm{C}_{5} \mathrm{H}_{6} \mathrm{O}(l)+\mathrm{O}_{2}(g) \longrightarrow \mathrm{CO}_{2}(g)+\mathrm{H}_{2} \mathrm{O}(g)\) (d) \(\mathrm{N}_{2}(g)+\mathrm{H}_{2}(g) \longrightarrow \mathrm{NH}_{3}(g)\) (e) \(\mathrm{K}_{2} \mathrm{O}(s)+\mathrm{H}_{2} \mathrm{O}(l) \longrightarrow \mathrm{KOH}(a q)\)

Step-by-Step Solution

Answer

(a) \(C_3H_6(g) + \frac{9}{2}O_2(g) \longrightarrow 3CO_2(g) + 3H_2O(g)\) - Combustion reaction (b) \(NH_4NO_3(s) \longrightarrow N_2O(g) + 2H_2O(g)\) - Decomposition reaction (c) \(C_5H_6O(l) + \frac{15}{2}O_2(g) \longrightarrow 5CO_2(g) + 3H_2O(g)\) - Combustion reaction (d) \(N_2(g) + 3H_2(g) \longrightarrow 2NH_3(g)\) - Combination reaction (e) \(K_2O(s) + H_2O(l) \longrightarrow 2KOH(aq)\) - Combination reaction

Step 1: (a) Balancing the equation

First, we balance the number of atoms for each element on both sides of the equation. This involves adding coefficients in front of the chemical compounds: \(C_3H_6(g) + \frac{9}{2}O_2(g) \longrightarrow 3CO_2(g) + 3H_2O(g)\) The balanced equation is now: \(C_3H_6(g) + \frac{9}{2}O_2(g) \longrightarrow 3CO_2(g) + 3H_2O(g)\) This is a combustion reaction, as it involves a hydrocarbon reacting with oxygen to produce carbon dioxide and water.

Step 2: (b) Balancing the equation

Balancing the atoms for each element on both sides of the equation: \(NH_4NO_3(s) \longrightarrow N_2O(g) + 2H_2O(g)\) The balanced equation is now: \(NH_4NO_3(s) \longrightarrow N_2O(g) + 2H_2O(g)\) This is a decomposition reaction, as a single compound breaks down into two or more simpler compounds.

Step 3: (c) Balancing the equation

Balancing the atoms for each element on both sides of the equation: \(C_5H_6O(l) + \frac{15}{2}O_2(g) \longrightarrow 5CO_2(g) + 3H_2O(g)\) The balanced equation is now: \(C_5H_6O(l) + \frac{15}{2}O_2(g) \longrightarrow 5CO_2(g) + 3H_2O(g)\) This is a combustion reaction, as it involves a hydrocarbon reacting with oxygen to produce carbon dioxide and water.

Step 4: (d) Balancing the equation

Balancing the atoms for each element on both sides of the equation: \(N_2(g) + 3H_2(g) \longrightarrow 2NH_3(g)\) The balanced equation is now: \(N_2(g) + 3H_2(g) \longrightarrow 2NH_3(g)\) This is a combination reaction, as simpler molecules (nitrogen and hydrogen) combine to form a more complex molecule (ammonia).

Step 5: (e) Balancing the equation

Balancing the atoms for each element on both sides of the equation: \(K_2O(s) + H_2O(l) \longrightarrow 2KOH(aq)\) The balanced equation is now: \(K_2O(s) + H_2O(l) \longrightarrow 2KOH(aq)\) This is a combination reaction, as simpler molecules (potassium oxide and water) combine to form a more complex molecule (potassium hydroxide).