Problem 53 - Chemistry: The Central Science

Question

Write balanced molecular and net ionic equations for the reactions of (a) manganese with dilute sulfuric acid, (b) chromium with hydrobromic acid, (c) tin with hydrochloric acid, (d) aluminum with formic acid, HCOOH.

Step-by-Step Solution

Answer

\( (a) \) Molecular: \(Mn + H_2SO_4 \rightarrow MnSO_4 + H_2 \) Net ionic: \(Mn + 2H^+ \rightarrow Mn^{2+} + H_2 \) \( (b) \) Molecular: \(2Cr + 6HBr \rightarrow 2CrBr_3 + 3H_2 \) Net ionic: \(2Cr + 6H^+ \rightarrow 2Cr^{3+} + 3H_2 \) \( (c) \) Molecular: \(Sn + 2HCl \rightarrow SnCl_2 + H_2 \) Net ionic: \(Sn + 2H^+ \rightarrow Sn^{2+} + H_2 \) \( (d) \) Molecular: \(2Al + 6HCOOH \rightarrow 2Al(HCOO)_3 + 3H_2 \) Net ionic: \(2Al + 6HCOOH \rightarrow 2Al(HCOO)_3 + 3H_2 \)

Step 1: (a) Manganese with dilute sulfuric acid: Molecular equation

First, write the unbalanced molecular equation: Mn + H2SO4 -> MnSO4 + H2. Now, balance the equation by ensuring equal numbers of each atom on both sides of the equation. The balanced molecular equation is: Mn + H2SO4 -> MnSO4 + H2.

Step 2: (a) Manganese with dilute sulfuric acid: Net ionic equation

Separate all strong electrolytes into their ions: Mn + 2H^+ + SO4^2- -> Mn^2+ + SO4^2- + H2. Now write the net ionic equation by removing the spectator ions: Mn + 2H^+ -> Mn^2+ + H2.

Step 3: (b) Chromium with hydrobromic acid: Molecular equation

Write the unbalanced molecular equation: Cr + HBr -> CrBr3 + H2. Now, balance the equation by ensuring equal numbers of each atom on both sides of the equation. The balanced molecular equation is: 2Cr + 6HBr -> 2CrBr3 + 3H2.

Step 4: (b) Chromium with hydrobromic acid: Net ionic equation

Separate all strong electrolytes into their ions: 2Cr + 6H^+ + 6Br^- -> 2Cr^3+ + 6Br^- + 3H2. Now write the net ionic equation by removing the spectator ions: 2Cr + 6H^+ -> 2Cr^3+ + 3H2.

Step 5: (c) Tin with hydrochloric acid: Molecular equation

Write the unbalanced molecular equation: Sn + HCl -> SnCl2 + H2. Now, balance the equation by ensuring equal numbers of each atom on both sides of the equation. The balanced molecular equation is: Sn + 2HCl -> SnCl2 + H2.

Step 6: (c) Tin with hydrochloric acid: Net ionic equation

Separate all strong electrolytes into their ions: Sn + 2H^+ + 2Cl^- -> Sn^2+ + 2Cl^- + H2. Now write the net ionic equation by removing the spectator ions: Sn + 2H^+ -> Sn^2+ + H2.

Step 7: (d) Aluminum with formic acid: Molecular equation

Write the unbalanced molecular equation: Al + HCOOH -> Al(HCOO)3 + H2. Now, balance the equation by ensuring equal numbers of each atom on both sides of the equation. The balanced molecular equation is: 2Al + 6HCOOH -> 2Al(HCOO)3 + 3H2.

Step 8: (d) Aluminum with formic acid: Net ionic equation

In this reaction, formic acid does not dissociate completely, so we do not separate it into its ions. The complete ionic equation is the same as the molecular equation: 2Al + 6HCOOH -> 2Al(HCOO)3 + 3H2. The balanced net ionic equation is: 2Al + 6HCOOH -> 2Al(HCOO)3 + 3H2.