Question

The balanced ionic equation for the reaction of K\(_2\)Cr\(_2\)O\(_7\) with Na\(_2\)SO\(_3\) in an acid solution is:

• A. Cr\(_2\)O\(_7^{2-}\)(aq) + SO\(_3^{2-}\)(aq) + 8H\(^+\)(aq) \( \to \) 2Cr\(^3+\)(aq) + SO\(_4^{2-}\)(aq) + 4H\(_2\)O(l)
• B. Cr\(_2\)O\(_7^{2-}\)(aq) + 3SO\(_3^{2-}\)(aq) + 2H\(^+\)(aq) \( \to \) 2Cr\(^3+\)(aq) + 3SO\(_4^{2-}\)(aq) + H\(_2\)O(l)
• C. 3Cr\(_2\)O\(_7^{2-}\)(aq) + 3SO\(_3^{2-}\)(aq) + 8H\(^+\)(aq) \( \to \) 6Cr\(^3+\)(aq) + 3SO\(_4^{2-}\)(aq) + H\(_2\)O(l)
• D. 3Cr\(_2\)O\(_7^{2-}\)(aq) + 3SO\(_3^{2-}\)(aq) + 2H\(^+\)(aq) \( \to \) 3Cr\(^3+\)(aq) + 3SO\(_4^{2-}\)(aq) + H\(_2\)O(l)
• E. Cr\(_2\)O\(_7^{2-}\)(aq) + 3SO\(_3^{2-}\)(aq) + 8H\(^+\)(aq) \( \to \) 2Cr\(^3+\)(aq) + 3SO\(_4^{2-}\)(aq) + 4H\(_2\)O(l)

Hint:

When balancing redox reactions, ensure both the number of electrons gained and lost is balanced.

Answer 1

Answer: (E)

Step 1: The balanced ionic equation involves the reduction of Cr\(_2\)O\(_7^{2-}\) to Cr\(^3+\) and the oxidation of SO\(_3^{2-}\) to SO\(_4^{2-}\).
Step 2: The stoichiometry of the equation is determined based on the electron balance and charge balance. 
Step 3: The correct balanced ionic equation is option (E).