Question

Balance the following equation in acidic solution:

\({\mathop {{\rm{Hg}}}\nolimits_2 ^{2 + }}{\rm{ + Ag}} \to {\rm{Hg}} + {\rm{A}}{{\rm{g}}^ + }\)

Short answer

The balance equation is \({\bf{Hg}} + {\bf{A}}{{\bf{g}}^ + } \to {\bf{2Ag}} + 2{\rm{H}}{{\rm{g}}^{2 + }}\)

Step-by-step solution

Define the balanced chemical reactions

A balanced chemical equation accurately describes the quantities of reactants and products in chemical reactions. The Law of Conservation of Mass states that mass is neither created nor destroyed in an ordinary chemical reaction.

Guidelines for balancing redox equations

Step 1. Write an unbalanced equation

Step 2. Separate the process into half reactions

a) Assign oxidation numbers for each atom

b) Identify and write out all redox couples in reaction

c) Combine these redox couples into two half-reactions

Step 3. Balance the atoms in each half reaction

a) Balance all other atoms except H and O

b) Balance the charge with H+ or OH-

c) Balance the oxygen atoms with H2O

Step 4: Make electron gain equivalent to electron loss in the half-reactions

Step 5: Add the half-reactions together

Step 6: Simplify the equation

Finally, check that the elements and charges are balanced.

a) Determine the Balance equation

Given unbalanced equation

\({\rm{A}}{{\rm{g}}^ + } + {\rm{Hg}} \to {\rm{H}}{{\rm{g}}^{2 + }} + {\rm{Ag}}\)

The two-half reaction: Oxidation \({\rm{Hg}} \to {\rm{H}}{{\rm{g}}^{2 + }}\)

All atoms are balanced so to balance charge add 2e on right

Oxidation \({\rm{Hg}} \to {\rm{H}}{{\rm{g}}^{2 + }} + 2\)e....equation 1

Reduction \(:{\rm{A}}{{\rm{g}}^ + } \to {\rm{Ag}}\)

To balance charge add 1e on left Reduction : \({\rm{A}}{{\rm{g}}^ + } + {\rm{e}} \to {\rm{Ag}}..\) equation 2

Multiple equation 2 with 2 to make electron for both reaction same

Reduction \(::2{\rm{A}}{{\rm{g}}^ + } + 2{\rm{e}} \to 2{\rm{Ag}}\)

Net balanced equation

Add Oxidation and reduction reaction

Net balanced reaction: \({\bf{Hg}} + {\bf{A}}{{\bf{g}}^ + } \to {\bf{2Ag}} + {\rm{H}}{{\rm{g}}^{2 + }}\)

So we see no water is present Thus water appear neither on product nor on reactant side so coefficient is 0. Number of electron transferred \( = 2\)