Chapter 4

Reactions in

Aqueous Solutions

&

Solution Stoichiometry

WHAT IS A SOLUTION ?

1. A HOMOGENEOUS Mixture of _______ or MORE Substances

Solvent + Solute = Solution

2. __________ varies

Reactions in Solution

• NEUTRALIZATION (Acid + _____)

• PRECIPITATION REACTIONS

• OXIDATION REDUCTION (______)

Acid Base Reaction

Example 1:

Hydrochloric Acid reacts with Sodium Hydroxide

1st Write the Reaction

HCl(aq) + NaOH(aq) � H2O + NaCl(aq)

2nd Balance Reaction

3rd Interpret Reaction

1 HCl (aq) +1 NaOH (aq) � H2O +1 NaCl (aq)

What is in solution?

1. HCl(aq) : HCl and ______

2. NaOH(aq) : NaOH and _____

What is reacting with what ?

HCl and ______

NOT THE WATER

Acid Base Reaction

Example 2:

Sulfuric Acid + Magnesium Hydroxide

1st Write the Reaction

H2SO4(aq) + Mg(OH)2(aq) � H2O + a salt

What is the salt ?

________= Magnesium Sulfate

H2SO4(aq) + Mg(OH)2(aq)�H2O + MgSO4(aq)

Is the reaction BALANCED ?

1 H2SO4(aq) +1 Mg(OH)2(aq)� __ H2O + 1 MgSO4(aq)

2nd Interpret the reaction

What is reacting with what ?

H2SO4 and Mg(OH)2 NOT the ______

What is an AQUEOUS Solution ?

WATER and ????? {see Table 4.1} SOLUBILITY RULES

WHAT IS IN SOLUTION ?

Molecules

or

Ions ?

Soluble Salts :: Solubility Rules

1. ALL Alkali Metals and Ammonium

Salts are SOLUBLE.

2. ALL Nitrates, PerChlorates and

Acetates are SOLUBLE

Now For The “Sometimes”

3. All Chlorides, Bromides, Iodides Soluble

EXCEPT Silver, Mercury, & Lead

4. See Text for Sulfates, Carbonates, etc.

ELECTROLYTE – A substance that dissolves

in water to produce IONS

Examples: HCl(aq), NaOH(aq), NaCl(aq)

NON ELECTROLYTE - A substance that Does

NOT produce IONS in water.

They remain as MOLECULES.

Examples: sugar, ethylene glycol

1. STRONG Electrolytes

A substance that completely _______

Strong Acids, Strong Bases, Soluble Salts

2. WEAK Electrolytes

Substance that does _____ completely ionize

Weak Acids, Weak Bases, SS Salts

ACIDS

Strong Acids

HCl(aq) � H+ (aq) + Cl- (aq) 100%

Weak Acids

HF(aq) ↔ H+ (aq) + ? - (aq)

note H+ (aq) ≡ H3O+ HYDRONIUM ION

ELECTROLYTESELECTROLYTESELECTROLYTESELECTROLYTES

1. STRONG ELECTROLYTES

Strong Acids [7]

Strong Bases [7]

Soluble Salts

2. WEAK ELECTROLYTES

Weak Acids / Bases

Slightly Soluble Salts

The 7 STRONG Acids

1. HCl(aq) ..……Hydrochloric Acid

2. HBr(aq)….…..Hydrobromic Acid

3. HI(aq)………..Hydroiodic Acid

4. HNO3(aq)…….Nitric Acid

5. H2SO4(aq)…….Sulfuric Acid

6. HClO3(aq)…….Chloric Acid

7. HClO4(aq)…….PerChloric Acid

ARRHENIUSARRHENIUSARRHENIUS BASES

1. STRONG Bases

NaOH (aq) � Na+ (aq) + OH- (aq) 100%

2. WEAK Bases

NH4OH(aq) ↔ NH4+ (aq) + ? - (aq)

note NH4OH ≡ NH3 (aq)

The 7 STRONG Bases

1. LiOH(aq)…….Lithium Hydroxide

2. NaOH(aq)……Sodium Hydroxide

3. KOH(aq)……..Potassium Hydroxide

4. RbOH(aq)……Rubidium Hydroxide

5. CsOH(aq)……Cesium Hydroxide

6. Ba(OH)2(aq)….Barium Hydroxide

7. Sr(OH)2(aq)…..Strontium Hydroxide

What do the following compounds do when

mixed with water ?

Magnesium Iodide

Aluminum Nitrate

Ammonium Sulfate

Perchloric Acid

Silver Chloride

MgI2 � Mg2+(aq) + ? I-(aq)

Al(NO3)3 � Al3+(aq) + ? NO3-(aq)

(NH4)2SO4� ? NH4+(aq) + SO4

2-(aq)

HClO4 � H+(aq) + ClO4-(aq)

??????????????????

1. Precipitation Reaction

2. Acid-Base Reaction

3. Oxidation-Reduction

Reaction

4. Active Metal + Acid

An INSOLUBLE Solid is Formed

Slightly IONIZED

Substance Formed

Change in Oxidation

State

A Gas is Formed

How do you recognize a PRECIPITATION

Reaction ?

INSOLUBLE SOLID FORMED

For example :

AgCl formed in reaction:

AgNO3 (aq) + NaCl (aq) � AgCl (s) + NaNO3 (aq)

1. Precipitation Reaction

2. Acid-Base Reaction

3. Oxidation-Reduction

Reaction

4. Active Metal + Acid

Insoluble Solid Formed

Slightly IONIZED

Substance Formed

Change in Oxidation

State

A Gas is Formed

ACID BASE REACTION ?

WATER IS FORMED

HCl (aq) + NaOH (aq) � H2O + NaCl (aq)

1. Precipitation Reaction

2. Acid-Base

3. Oxidation-Reduction

Reaction

4. Active Metal + Acid

Insoluble Solid Formed

Slightly IONIZED

Substance Formed

Change in Oxidation

State

A Gas is Formed

How do you recognize an

Oxidation Reduction Reaction ?

CHANGE IN OXIDATION STATE

MUST KNOW OXIDATION “RULES”

See Page 139 – 140 Text

1. Precipitation Reaction

2. Acid-Base Reaction

3. Oxidation-Reduction

Reaction

4. Active Metal

+ Acid

An INSOLUBLE Solid is Formed

Slightly IONIZED

Substance Formed

Change in Oxidation

State

A Gas is Formed

Active Metal + Acid Reaction

Hydrochloric acid reacts with zinc metal to

produce Hydrogen gas and zinc chloride

1st Write Reaction

Zn (solid) + HCl (aq) → ___ (gas) + ____(aq)

2nd Balance Reaction

1 Zn (s) + 2 HCl (aq) → 1 H2 (g) + 1 ZnCl2(aq)

3rd Interpret Reaction

1 mol Zn needed for every 2 moles of HCl

forming 1 mol H2 and 1 mol ZnCl2

How much HCl(aq) is need to convert 65.4 g of

Zn to hydrogen gas and zinc chloride?

How many moles of Zn are present ?

How many moles of HCl are required ?

From: 1 Zn + 2 HCl (aq)→ H2+ ZnCl2(aq)

2 x 1.00 = _____ moles HCl needed

.001 39.65

1 x 4.65 =

grams

molesgrams

MOLECULAR WEIGHTMOLECULAR WEIGHTMOLECULAR WEIGHT

is the CONVERSION FACTORBetween

MOLES of a Solid

and

The WEIGHT of the Solid

( ) MolesGrams

MolesGrams =×

?

1___

How much HCl(aq) is need to convert 6.54 g of

Zn to hydrogen gas and zinc chloride?

How many moles of Zn are present ?

How many moles of HCl are required ?

From: 1 Zn + 2 HCl (aq)→ H2+ ZnCl2(aq)

2 x 0.100 = ____ moles HCl needed

0010. 39.65

1 x 54.6 =

grams

molesgrams

How much HCl(aq) is need to convert 10.0g of

Zn to hydrogen gas and zinc chloride?

How many moles of Zn are present ?

How many moles of HCl are required ?

From: 1 Zn + 2 HCl (aq)→ H2+ ZnCl2(aq)

2 x 0.153 = ____ moles HCl needed

153.0 39.65

1 x 0.10 =

grams

molesgrams

What volume of 2.50 M HCl(aq) is needed to convert 10.0 g of Zn to zinc chloride ?

CONCENTRATIONS IN SOLUTIONS

Molarity

MOLARITY is a

CONVERSION FACTORCONVERSION FACTORCONVERSION FACTORCONVERSION FACTOR

BETWEEN

NUMBER OF MOLES OF SOLUTE

AND

THE VOLUME OF SOLUTION

Molarity (M)

Memorize the definition

Molarity = Moles of Solute

Liters of Solution

or

Moles Solute = Molarity x Volume

1 Zn + 2 HCl (aq)→ H2+ ZnCl2(aq)( 2.50 M HCl(aq) )

For HCl(aq) need 2 x 0.153 = 0.306 moles

Molarity x Volume = moles

mLMolarity

molesvolume 122

50.2

306.0 ===

LIMITING REAGENT ?LIMITING REAGENT ?LIMITING REAGENT ?

1 Zn + 2 HCl (aq)→ H2+ ZnCl2(aq)

What is the limiting reagent if 122 mL of 2.50 M HCl(aq) is combined with 10.0 g of Zn to zinc chloride ?

(a) Zn

(b) Water

(c) HCl

(d) There isn’t one

Limiting Reagent

What is the limiting reagent if 122 mL

of 2.50 M HCl(aq) is combined with

1.0 g of Zn to zinc chloride ?

(a)Zn

(b)Water

(c) HCl

(d) There isn’t one

Limiting Reagent

What is the limiting reagent if 125 mL

of 2.50 M HCl(aq) is combined with

10.0 g of Zn to zinc chloride ?

(a)Zn

(b)water

(c) HCl

(d) There isn’t one

Limiting Reagent

What is the limiting reagent if 122 mL

of 2.50 M HCl(aq) is combined with

20.0 g of Zn to zinc chloride ?

(a)Zn

(b)water

(c) HCl

(d) There isn’t one

Limiting Reagent

What is the limiting reagent if 120 mL

of 2.50 M HCl(aq) is combined with

10.0 g of Zn to zinc chloride ?

(a)Zn

(b)water

(c) HCl

(d) There isn’t one

OXIDATION REDUCTION (Redox) REACTIONS

Examples

HgO(s) � Hg(liq) + O2 (gas)

Fe(s) + O2(gas) → Fe

2O

3(s)

Zn(s) + HCl(aq) → H2(g) + ZnCl

2(aq)

How do you recognize an

Oxidation Reduction Reaction ?

MUST KNOW OXIDATION “RULES”

See Page 139 – 140 Text

1. EACH ATOM in a PURE ELEMENT

Has An OXIDATION NUMBER of

ZERO

. 2. For IONS Consisting of a SINGLE

ATOM, the Ox Num IS EQUAL

To THE CHARGE ON THE ION

3. F ALWAYS Has an Ox Num of –1

In ALL Of Its COMPOUNDS

4. Cl, Br, and I are – 1 EXCEPT when

combined with O or F

5. H is + 1 and O is – 2 EXCEPT in

Hydrides (CaH2) & Peroxides (H2O2)

6 The ALGEBRAIC SUM of the Oxidation

Numbers in a NEUTRAL Compound

MUST be ZERO

Prob 4.40 Determine the oxidation number for

1. Ti in TiO2

2. Sn in SnCl2

3. C in C2O42-

4. N in (NH4)2SO4

5. N in HNO3

6. Cr in Cr2O72-

____

____

____

____

____

____

OXIDATION Number of Underlined Atom

1. O 2

2. H2 O

3. H2 O 2

4. KClO 4

5. H 2

6. HCl

7. CaH 2

8. H 2O 2

____

____

____

____

____

____

____

____

OXIDATION Number of Underlined Atom

1 H Cl O4

2. Cl O3-

3. Cl F

4. Cl 2

____

____

____

____

For Redox Reactions

• What is The OXIDATION NUMBER

For EACH Element Present ?

• What is OXIDIZED ?

• What is REDUCED ?

• What is The OXIDIZING AGENT ?

• What is The REDUCING AGENT ?

1. OXIDATION – LOSS of electrons

2. REDUCTION – GAIN of electrons

• AN OXIDIZING AGENT “CAUSES”

OXIDATION

• A REDUCING AGENT “CAUSES”

REDUCTION

Zn(s) + 2 HCl(aq) → H2(g) + ZnCl2(aq)

What is The OXIDATION NUMBER For

EACH Element Present ?

What is OXIDIZED ? ________

What is REDUCED ? ________

What is the Oxidizing AGENT ? ________

What is the Reducing AGENT ? ________

Classify Each Reaction As Either(a) Precipitation, (b) Neutralization or

(c) Oxidation-Reduction

Hg(NO3)2(aq) + NaI(aq) � NaNO3(aq) + HgI2(S)

H3PO4(aq) + KOH(aq) � H2O(liq) + K3 PO4(aq)

HgO(s) + heat � Hg(liq) + O2 (gas)

CH4(gas) + O2 (gas) � CO2(gas) + H2O(liq)

How do you recognize a

Precipitation Reaction ?

INSOLUBLE SOLID FORMED

Will the following reaction occur ?

A solution of Silver Nitrate is mixed

with a solution of Sodium Chloride

_______ ?

How do you know ?

______ formed in reaction:

AgNO3 (aq) + NaCl (aq) � _____(s) + NaNO3 (aq)

Will the following reaction occur ?

NaOH(aq) + HClO4(aq) � ??

______

How do you know ?

______ formed in reaction

Will the following reaction occur ?

Pb(NO3)2 + Na2SO4 � ??

_______ ?

How do you know ?

______ formed in reaction:

Will the following reaction occur ?

AgClO4 + Na2S → ??

_______ ?

How do you know ?

______ formed in reaction:

Will the following reaction occur ?

AgClO4 + NaNO3 → ??

_______ ?

How do you know ?

______ formed in reaction:

• MOLECULARMOLECULARMOLECULARMOLECULAR Uses The Full Formula

Of Reactants and Products

• IONIC IONIC IONIC IONIC – A Reaction Written So Ions

Are Explicitly Shown

• NET IONICNET IONICNET IONICNET IONIC – Spectator Ions Are

Removed From Ionic Equation

Write & Balance Molecular, Ionic

And Net Ionic Equations For :

Hg(NO3)2(aq) + NaI(aq) � ?????????????

H2SO4(aq) + KOH(aq) � ???????????????

CH4(gas) + O2 (gas) � ??????????????

Preparing Solutions

1. Preparing Solutions of Known Concentrations

2. Preparing a Solution by Dilution

How Many Moles Of each of the following

are Needed To Make 1.O Liter of 1.0 M

Solution ?

KCl ; NaHCO3 ; Na2CO3 ;Fe2O3

How Many Moles Of each of the above are Needed To Make 1.O Liter of 1.5 M Solutions ?

How Many MOLES Of Na2CO3

Needed To Make 2.O Liters of 1.5 M Solution ?

• Need 1.5 Moles of Na2CO

3to make one Liter

of 1.5 M

• ???????????????????????????

• So Need 2 x 1.5 Moles = 3.0 Moles to make

2.0 Liters

How Many GRAMSGRAMSGRAMSGRAMS Of Na2CO3 Are

Needed To Make 2.O L Of 1.5 M Solution

1st : How many moles ?

2nd : How do you go from moles to grams?

What is formula Weight for Na2CO

3 ?

2 x 23 + 12 + 3 x 16 = 106 g / mole

3.0 moles x 106 g / mole = (318g)

Preparing Solutions of Known Concentrations

An experiment requires ½ Liter of a

0.0200 M solution of Na2 CO3

You are given a bottle of solid Na2 CO3

some distilled water, and a 500 mL

volumetric flask. Describe how to

make the required solution.

Molarity x Volume = moles

Need ½ Liter of a 0.0200 Molar solution

Molarity x Volume = moles of Solute

(0.0200 M)(0.500 Liters) = 1.00 x 10-2 moles of Na2 CO3

How do you convert from moles to grams?

Formula weight of Na2 CO3 = 106.0 g / mole

(1.00 x 10-2 moles) x (106.0 g / mole) = 1.06 grams

So what do you do?

1. Weigh 1.06 grams of Na2 CO3

2. Transfer the Na2 CO3 to the flask

3. Add water until 500 mL is obtained

Preparing a Solution by Dilution

• An experiment calls for you to use 250

mL of 1.00 M NaOH, but you are given

a large bottle of 2.00 M NaOH.

• Describe how to make the 1.00 M

NaOH solution.

Preparing a Solution by Dilution

• Need 250 mL of 1.00 M NaOH

• Given a large bottle of 2.00 M NaOH.

• How do you make a 1.00 M NaOH solution.

M1 V1 = M2 V2 = moles of Solute

(250 mL) (1.00 M ) = ( ? mL ) (2.00 M )

Volume = 125 mL of 2.00 M NaOH

So what do you do?

1. Measure 125 mL of 2.00 M NaOH

2. Add water until 250 mL is obtained