Problem 26 - Chemistry: The Central Science

Question

Write balanced equations for each of the following reactions (some of these are analogous to reactions shown in the chapter). (a) Aluminum metal reacts with acids to form hydrogen gas. (b) Steam reacts with magnesium metal to give magnesium oxide and hydrogen. (c) Manganese(IV) oxide is reduced to manganese(II) oxide by hydrogen gas. (d) Calcium hydride reacts with water to generate hydrogen gas.

Step-by-Step Solution

Answer

The balanced equations for the given reactions are: a) \(2 Al (s) + 6 HCl (aq) \rightarrow 2 AlCl_3 (aq) + 3 H_2 (g)\) b) \(Mg (s) + H_2O (g) \rightarrow MgO (s) + H_2 (g)\) c) \(MnO_2 (s) + 2 H_2 (g) \rightarrow MnO (s) + 2 H_2O (g)\) d) \(CaH_2 (s) + 2 H_2O (l) \rightarrow Ca(OH)_2 (aq) + 2 H_2 (g)\)

Step 1: Reaction a: Aluminum metal reacts with acids to form hydrogen gas

In this case, we consider hydrochloric acid as a representative for acids. The reaction can be written as: Al (s) + HCl (aq) -> AlCl3 (aq) + H2 (g) Now we need to balance the equation: 2 Al (s) + 6 HCl (aq) -> 2 AlCl3 (aq) + 3 H2 (g)

Step 2: Reaction b: Steam reacts with magnesium metal to give magnesium oxide and hydrogen

Write the reaction: Mg (s) + H2O (g) -> MgO (s) + H2 (g) Balance the equation: Mg (s) + H2O (g) -> MgO (s) + H2 (g) In this case, the equation is already balanced.

Step 3: Reaction c: Manganese(IV) oxide is reduced to manganese(II) oxide by hydrogen gas

Write the reaction: MnO2 (s) + H2 (g) -> MnO (s) + H2O (g) Balance the equation: MnO2 (s) + 2 H2 (g) -> MnO (s) + 2 H2O (g)

Step 4: Reaction d: Calcium hydride reacts with water to generate hydrogen gas

Write the reaction: CaH2 (s) + H2O (l) -> Ca(OH)2 (aq) + H2 (g) Now we need to balance the equation: CaH2 (s) + 2 H2O (l) -> Ca(OH)2 (aq) + 2 H2 (g)