7.4.5: Practice Classifying Reactions

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Classify Reactions

Exercise \(\PageIndex{1}\)

Classify each reaction below as combination, decomposition, single displacement, double displacement, or combustion.

CaCO₃_(s) \(\rightarrow\) CO₂_(g) + CaO _(s)

Answer: decomposition

2 N₂_(g) + 5 O₂ _(g) \(\rightarrow\) 2 N₂O₅_(g)

Answer: combination

C₅H₁₀O_(l) + 7 O₂ _(g) \(\rightarrow\) 5 CO₂_(g) + 5 H₂O _(g)

Answer: combustion

ZnCl₂_(aq) + 2 AgNO₃_(aq) \(\rightarrow\) Zn(NO₃)_{2 (aq)} + 2 AgCl _(s)

Answer: double displacement

Cl₂_(g) + 2 KBr_(aq) \(\rightarrow\) Br_{2 (l)} + 2 KCl _(aq)

Answer: single displacement

2 H₂_(g) + O₂ _(g) \(\rightarrow\) 2 H₂O _(g)

Answer: combination

Mg _(s) + HCl _(aq) \(\rightarrow\) MgCl₂_(aq) + H_{2 (g)}

Answer: single displacement

Total Ionic and Net Ionic Equations

Exercise \(\PageIndex{1}\)

Give the total ionic equation ("complete ionic equation") and the net ionic equation for each reaction below.

ZnCl₂_(aq) + 2 AgNO₃_(aq) \(\rightarrow\) Zn(NO₃)_{2 (aq)} + 2 AgCl _(s)

Total Ionic: Zn²⁺_(aq) + 2 Cl^1–_(aq) + 2 Ag¹⁺_(aq) + 2 NO₃^1–_(aq) \(\rightarrow\) Zn²⁺_(aq) + 2 NO₃^1–_(aq) + 2 AgCl _(s)

Net Ionic: 2 Cl^1–_(aq) + 2 Ag¹⁺_(aq) \(\rightarrow\) 2 AgCl _(s)

H₃PO₄_(aq) + 3 NaOH_(aq) \(\rightarrow\) Na₃PO_4 (aq) + 3 H₂O _(l)

Total Ionic: 3 H¹⁺_(aq) + PO₄^3–_(aq) + 3 Na¹⁺_(aq) + 3 OH^1–_(aq) \(\rightarrow\) 3 Na¹⁺_(aq) + PO₄^3–_(aq) + 3 H₂O _(l)

Net Ionic: 3 H¹⁺_(aq) + 3 OH^1–_(aq) \(\rightarrow\) 3 H₂O _(l)

Precipitation Reactions

Exercise \(\PageIndex{1}\)

Which of the following compounds would not be soluble in water (and would form a solid precipitate)?

LiCl Pb(NO₃)₂ BaBr₂ CaSO₄ AgBr Zn(C₂H₃O₂)₂ MgSO₄ CaCl₂ K₂CO₃ NiPO₄

Answer: CaSO₄ AgBr NiPO₄

For each of the reactions below, predict the products formed. Use the correct chemical formulas. Then balance the reaction and tell which product would be soluble ("aq" aqueous solution) and which would be insoluble ("s" solid precipitate).

CuCl₂_(aq) + KOH _(aq) \(\rightarrow\)

Answer: CuCl₂_(aq) + 2 KOH _(aq) \(\rightarrow\) 2 KCl _(aq) + Cu(OH)_{2 (s)}

CaCl₂_(aq) + Pb(NO₃)₂ _(aq) \(\rightarrow\)

Answer: CaCl₂_(aq) + Pb(NO₃)₂ _(aq) \(\rightarrow\) Ca(NO₃)_{2 (aq)} + PbCl₂_(s)

Ba(ClO₃)₂_(aq) + Li₂SO₄ _(aq) \(\rightarrow\)

Answer: Ba(ClO₃)₂_(aq) + Li₂SO₄ _(aq) \(\rightarrow\) 2 LiClO₃_(aq) + BaSO₄ _(s)

Oxidation and Reduction

Exercise \(\PageIndex{1}\)

For each reaction below, tell which element is being oxidized and which is being reduced.

Mg _(s) + HCl _(aq) \(\rightarrow\) MgCl₂_(aq) + H_{2 (g)}

Answer: Mg is being oxidized (0 to +2 charge), Cl has no change (–1 to –1 charge), H is being reduced (+1 to 0 charge)

2 Al _(s) + 3 Br₂ _(l) \(\rightarrow\) 2 AlBr_{3 (s)}

Answer: Al is being oxidized (0 to +3 charge), Br is being reduced (0 to –1 charge)

Cl₂_(g) + 2 KBr_(aq) \(\rightarrow\) Br_{2 (l)} + 2 KCl _(aq)

Answer: Cl is being reduced (0 to –1 charge), K is not changing (+1 to +1 charge), Br is being oxidized (–1 to 0 charge).