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Ionic equations

A chemical equation shows the number of atoms and molecules of the reactants and products.

Also shows physical state of reactants and products.

However, does not show clearly the reactions of ionic compounds.

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Ionic equations

An ionic equation shows only the ions taking part in the reaction and leaves out the ions that do not

react.

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Writing ionic equations

Procedure is similar as writing chemical equations.

A) Ionic compounds when dissolved in water dissociate completely into ions.

B) Spectator ions i.e ions that do not take part in the reaction are omitted on both sides of the

ionic equation.

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Writing ionic equations Example 1

Step 1 Write word equation and chemical formula. Silver nitrate + sodium chloride silver chloride

+ sodium nitrate

AgNOAgNO33 (aq) + NaCl (aq) (aq) + NaCl (aq) AgCl (s) + Na AgCl (s) + Na

NONO3 (aq)(aq)

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Writing ionic equations Example 1

Step 2 Write formula of ions formed

AgAg++ (aq) + NO (aq) + NO33-- (aq) (aq) + + NaNa++ (aq) + Cl (aq) + Cl-- (aq) (aq)

AgCl (s) + AgCl (s) + NaNa++ (aq) + (aq) + NONO3- (aq)(aq)

AgNOAgNO33 (aq) + NaCl (aq) (aq) + NaCl (aq) AgCl (s) + AgCl (s) +

NaNa NONO3 (aq)(aq)

Not able to dissolve in water to form ions

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Writing ionic equations Example 1 Step 3 Omit spectator ions (NONO33

-- and and NaNa++ appear both sides. Do not take part in the reaction. Can be cancelled)

AgAg++ (aq) + NO (aq) + NO33-- (aq) (aq) + + NaNa++ (aq) + Cl (aq) + Cl-- (aq) (aq)

AgCl (s) + AgCl (s) + NaNa++ (aq) + (aq) + NONO3- (aq)(aq)

AgAg++ (aq) (aq) + Cl+ Cl-- (aq) (aq) AgCl (s) AgCl (s)

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Writing ionic equationsExample 2

Step 1 Write word equation and chemical formula. Sodium hydroxide + hydrochloric acid sodium

chloride + water

NaOH (aq)+ HCl (aq) NaOH (aq)+ HCl (aq) NaCl (aq) NaCl (aq)

+ H+ H22O (l)O (l)

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Writing ionic equationsExample 2

Step 2 Write formula of ions formed

NaNa++ (aq) + OH (aq) + OH-- (aq) (aq) + + HH++ (aq) + Cl (aq) + Cl-- (aq) (aq)

NaNa++ (aq) + (aq) + ClCl- (aq) + (aq) + HH22O (l)O (l)

NaOH (aq)+ HCl (aq) NaOH (aq)+ HCl (aq) NaCl (aq) NaCl (aq)

+ H+ H22O (l)O (l)

Covalent compound. Does not form ions

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Writing ionic equationsExample 2 Step 3 Omit spectator ions (Na++ and Cl and Cl-- appear both

sides. Do not take part in the reaction. Can be cancelled)

HH++ (aq) + OH (aq) + OH-- (aq) (aq) H2O (l)

NaNa++ (aq) + OH (aq) + OH-- (aq) (aq) + + HH++ (aq) + Cl (aq) + Cl-- (aq) (aq)

NaNa++ (aq) + (aq) + ClCl- (aq) + (aq) + HH22O (l)O (l)

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Writing ionic equationsExample 3

Step 1 Write word equation and chemical formula. Sodium carbonate + dilute hydrochloric acid

sodium chloride + water + carbon dioxide

NaNa22COCO33 (aq)+ 2HCl (aq) (aq)+ 2HCl (aq) 2NaCl 2NaCl (aq)(aq) + H+ H22O (l) + COO (l) + CO22 (g) (g)

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Writing ionic equationsExample 3

Step 2 Write formula of ions formed

22NaNa++ (aq) + CO (aq) + CO33-- (aq) (aq) + + 22HH++ (aq) + (aq) + 22ClCl--

(aq)(aq) 22NaNa++ (aq) + (aq) + 22ClCl- (aq) + (aq) + HH22O (l) + O (l) +

COCO22 (g) (g)

NaNa22COCO33 (aq)+ (aq)+ 22HCl (aq) HCl (aq) 22NaCl NaCl (aq)(aq) + H+ H22O (l) + COO (l) + CO22 (g) (g)

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Writing ionic equationsExample 3 Step 3 Omit spectator ions (Na++ and Cl and Cl-- appear both

sides. Do not take part in the reaction. Can be cancelled)

2H2H++ (aq) + CO (aq) + CO33-- (aq) (aq) CO CO22 (g) + (g) + H2O (l)

22NaNa++ (aq) + CO (aq) + CO33-- (aq) (aq) + + 22HH++ (aq) + (aq) + 22ClCl--

(aq)(aq) 22NaNa++ (aq) + (aq) + 22ClCl- (aq) + (aq) + HH22O (l) + O (l) +

COCO22 (g) (g)

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1 Magnesium + sulfuric acid magnesium sulfate + hydrogen

2 Sodium hydroxide + nitric acid Sodium nitrate + water

Write balanced chemical equations and then the ionic equations (with state symbols) for the following questions.

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3 Magnesium oxide + hydrochloric acid Magnesium chloride + water

4 Silver nitrate solution + potassium iodide solution silver iodide (AgI is insoluble) + potassium nitrate

Write balanced chemical equations and then the ionic equations (with state symbols) for the following questions.

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Answers in red box

(take a peek only after you’ve done the questions in your notes. Your integrity counts!)

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1. Magnesium + sulfuric acid magnesium sulfate + hydrogen

Mg (s) + H2SO4 (aq) MgSO4 (aq) + H2 (g)

Mg (s) + 2H+ (aq) + SO42- (aq) Mg2+ (aq) +

SO42- (aq) + H2 (g)

Mg (s) + 2H+ (aq) Mg2+ (aq) + H2 (g)

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2. Sodium hydroxide + nitric acid Sodium nitrate + water

NaOH (aq) + HNO3 (aq) NaNO3 (aq) + H2O (l)

Na+ (aq) + OH- (aq) + H+ (aq) + NO3- (aq)

Na+ (aq) + NO3- (aq) + H2O (l)

OH- (aq) + H+ (aq) H2O (l)

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3. Magnesium oxide + hydrochloric acid Magnesium chloride + water

MgO (s) + 2HCl (aq) MgCl2 (aq) + H2O (l)

MgO (s) + 2H+ (aq) + 2Cl- (aq) Mg2+ (aq) +

2Cl- (aq) + H2O (l)

MgO (s) + 2H+ (aq) Mg2+ (aq) + H2O (l)

4. Silver nitrate + potassium iodide silver iodide + potassium nitrate

AgNO3 (aq) + KI (aq) AgI (s) + KNO3 (aq)

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Ag+ (aq) + NO3- (aq) + K+ (aq) + I- (aq)

AgI (s) + K+ (aq) + NO3- (aq)

Ag+ (aq) + I- (aq) AgI (s)