# Balancing Redox Reactions 2 (Worksheet)


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Work in groups on these problems. You should try to answer the questions without referring to your textbook. If you get stuck, try asking another group for help.

The half-equation method separates the oxidation and reduction of a redox reaction in half reactions. Overall scheme for the half reaction method:

• Step 1: Split reaction into half-reactions (reduction and oxidation)
• Step 2: Balance the charge or oxidation number with electrons
• Step 3: Balance $$\ce{O}$$ by adding $$\ce{H2O}$$
• Step 4: Balance $$\ce{H}$$ by adding $$\ce{H^{+}}$$
• Step 5: Multiply by some integer to make electrons (lost) = electrons (gained)
• Step 6: Add half equations and cancel substances on both sides
• Step 7: (only in basic solution): add $$\ce{OH^{-}}$$ and cancel $$\ce{H_2O}$$
• Step 8: Check atom balance and charge balance on both sides of the equation!

## Q1

$\ce{Zn(s) + H^{+} (aq) -> Zn^{2+} + H2(g)} \tag{in acidic solution}$

______________________________________________________ (reduction half-reaction)

______________________________________________________ (oxidation half-reaction)

______________________________________________________ (overall)

## Q2

$\ce{ I^{-} (aq) + NO2^{-}(aq) -> I2(s) + NO(g)} \tag{in acidic solution}$

______________________________________________________ (reduction half-reaction)

______________________________________________________ (oxidation half-reaction)

______________________________________________________ (overall)

## Q3

$\ce{ MnO4^{-}(aq) + Cl^{-}(aq) -> Mn^{2+}(aq) + Cl2(g)} \tag{acidic solution}$

______________________________________________________ (reduction half-reaction)

______________________________________________________ (oxidation half-reaction)

______________________________________________________ (overall)

Do the same reaction in basic solution:

______________________________________________________ (overall)

## Q4

$\ce{Br2(l) -> BrO3^{-}(aq) + Br^{-}(aq)} \tag{basic solution}$

______________________________________________________ (reduction half-reaction)

______________________________________________________ (oxidation half-reaction)

______________________________________________________ (overall)

## Q5

$\ce{CrO4^{-} + S^{2-} -> Cr^{3+} + SO4^{2-}} \tag{in acidic solution}$

______________________________________________________ (reduction)

______________________________________________________ (oxidation)

______________________________________________________ (overall)

## Q6

$\ce{H2O2 + NO2^{}- -> H2O + NO3^{-}} \tag{acidic solution}$

______________________________________________________ (reduction half-reaction)

______________________________________________________ (oxidation half-reaction)

______________________________________________________ (overall)

Balancing Redox Reactions 2 (Worksheet) is shared under a not declared license and was authored, remixed, and/or curated by Mark Draganjac.