Final acid and bases rev

Walter Waswa

WALTER WASWA1

ACIDArrhenius : an acid is a material that can

release a proton or hydrogen ion (H +)Brønsted : an acid is a material that donates

a proton.Lewis definitions are: Acids are electron pair

acceptors CONUGATE BASE:Each acid has a proton

available (an ionizable hydrogen) and another part.

When the acid ionizes, the hydrogen ion is the acid and the rest of the original acid is the conjugate base.

Nitric acid, HNO 3, dissociates (splits) into a hydrogen ion and a nitrate ion.

The hydrogen almost immediately joins to a water molecule to make a hydronium ion.

The nitrate ion is the conjugate base of the hydrogen ion.

In the second part of the reaction, water is a base (because it can accept a proton) and the hydronium ion is its conjugate acid.

HNO3+ H2O (NO3)- + (H3O)+

ACID BASE CONUGATE BASES CONJUGATE ACID

PROPERTIES OF ACIDS1. Acids release a hydrogen ion into

water (aqueous) solution2. Acids neutralize bases in a

neutralization reaction. 3. Acids corrode active metals. 4. Acids turn blue litmus to red. 5. Acids taste sour..

Common Acids:

All others considered Weak (examples)

Strong Acids The Formula

Sulphuric acidHydrochloric acidHybrobromic acidHydroiodic acidNitric acidPerchloric acid

H2SO4

HClHBrHIHNO3

HClO4

Acetic acid (vinegar) HC2H3O2

Carbonic acid HCO3

Weak Acid The Formula

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basesArrhenius: is a material that can donate a

hydroxide ion (OH-

Brønsted: base is a material that can accept a proton

Lewis: bases are electron pair donors.

Properties of bases1. Bases release a hydroxide ion into

water solution2. Bases neutralize acids in a

neutralization reaction. 3. Bases denature protein. 4. Bases turn red litmus to blue. 5. Bases taste bitter

Strong Bases The Formulae

Lithium hydroxideSodium hydroxidePotassium hydroxideRubidium hydroxideCaesium hydroxideBarium hydroxideCalcium hydroxideStrontium hydroxide

LiOHNaOHKOHRbOHCsOHBa(OH)2

Ca(OH)2

Sr(OH)2

Common Bases:

(Hydroxides of Group 1 and Group 2 Metals are STRONG)

All others are WEAKWALTER WASWA9

STRENGTH OF ACIDS AND BASESA strong acid is one that fully ionizes egHNO3 - nitric acid

HCl1 - hydrochloric acidH2SO4 - sulfuric acid HClO4 - perchloric acid HBr1 - hydrobromic acidHI1 - hydroiodic acid

Incompletely ionized acids are called weak acids.

because there is a smaller concentration of ionized hydrogens available in the solution

differences in concentration of the entire acid will be termed dilute or concentrated

ones that completely ionize into hydroxide ions and a conjugate acid=Strong base

All of the bases of Group I and Group II metals except for beryllium are strong bases

The bases of Group I metals are all monobasic. The bases of Group II metals are all dibasic. Aluminum hydroxide, Al(OH)3 is tribasic.

Any material with two or more ionizable hydroxyl groups would be called polybasic

Most of the alkaline organic compounds have an amino group -(NH2) rather than an ionizable hydroxyl group.

The amino group attracts a proton (hydrogen ion) to become -(NH3 )+.

(The dash before the (NH3)+ or (NH2) indicates a single bonding electron, so this is attached to something else by a covalent bond.)

By the Lowry- Brønsted definition, an amino group definitely acts as a base, and the effect of removing hydrogen ions from water molecules is the same as adding hydroxide ions to the solution.

Ph

The pH of a solution is the negative log of the hydrogen ion concentration.

The hydrogen ion concentration is inversely proportional to the hydroxide ion concentration, and the two of them multiplied together give the number 1 E-14.

WEAK ACID AND WEAK BASESWe can write the chemical equation for the

dissociation of a weak acid, using 'A-' to represent the conjugate base, as;

HA A- + H+

we can write the chemical equation for the dissociation of a weak base, using 'X+' to represent the conjugate acid, as;

XOH (OH)- + X+

The equilibrium expression for the dissociation of a weak acid is

The dissociation constant of an acid is equal to the concentration of hydrogen ions times the concentration of the conjugate base of the acid divided by the concentration of un-ionized acid."

Equilibrium expression for a weak base reads: "The dissociation constant of a base equals concentration of hydroxide ions times concentration of conjugate acid divided by the concentration of un-ionized base."

The kA of an acid or the kB of a base are properties of that acid or base at the given temperature. The temperature at which these dissociation constants are listed is usually near room temperature.

INDICATORS An indicator is a compound that will change color in the presence of an acid or base

litmus phenophthalein

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Acid-red Base-blue Neutral-purple

Acid-colourles Base-pink Neutral-colourles

Methyl orange

Acid-pinkBase-yellowNeutral-orange

Universal indicatorP 59 sec.chem f1 5th ed.by klb 2003

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Acid Strength and pKa:

Acids

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Figure 2.5 Summary of the factors that determine acidity

Acids and BasesFactors that Determine Acid Strength

2major Factors that affect strength of an acid

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1) Bond strength :The strength of the bond between the acidic

proton and the rest of the molecule will have an effect on acidity.

The weaker the bond, the more acidic the acid will be generally.

2) Bond polarity :The polarity of a bond is the distribution of the electrons between the two bonded atoms.

If the electrons are fairly equally distributed, the bond is not very polar. As the electron distribution gets weighted towards one atom, the bond becomes more polar .

A highly polar bond between an acidic hydrogen and another atom tends to make it more easy for the proton to leave the molecule than would

happen for a non-polar bond.

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Brønsted-Lowry Theory of Acids & BasesConjugate Acid-Base Pairs

General Equation

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Brønsted-Lowry Theory of Acids & Bases

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Brønsted-Lowry Theory of Acids & Bases

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Brønsted-Lowry Theory of Acids & BasesNotice that water is both an acid & a base = amphoteric

Reversible reaction

ELECTROLYTESELECTROLYTES

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Electrolytes are species which conducts electricity when dissolved in water. Acids, Bases, and Salts are all electrolytes.

Salts and strong Acids or Bases form Strong Electrolytes. Salt and strong acids (and bases) are fully dissociated therefore all of the ions present are available to conduct electricity.

HCl(s) + H2O H3O+ + Cl-

Weak Acids and Weak Bases for Weak Electrolytes. Weaks electrolytes are partially dissociated therefore not all species in solution are ions, some of the molecular form is present. Weak electrolytes have less ions avalible to conduct electricity.

NH3 + H2O NH4+ + OH-

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Acids & BasesAcids & Bases

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STRONG vs WEAKSTRONG vs WEAK_ _ completely ionizedcompletely ionized _ partially ionized_ partially ionized

_ strong electrolyte_ strong electrolyte _ weak electrolyte_ weak electrolyte

_ ionic/very polar bonds_ ionic/very polar bonds _ some _ some covalent bondscovalent bonds

Strong AcidsStrong Acids:: Strong Bases:Strong Bases:HClOHClO44 LiOHLiOH

HH22SOSO44 NaOHNaOH

HIHI KOHKOHHBrHBr Ca(OH)Ca(OH)22

HClHCl Sr(OH)Sr(OH)22

HNOHNO33 Ba(OH)Ba(OH)22


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One ionizable proton:

HCl → H+ + Cl- Two ionizable protons:

H2SO4 → H+ + HSO4-

HSO4- → H+ + SO4

2-

Three ionizable protons:

H3PO4 → H+ + H2PO4–

H2PO4- → H+ + HPO4

2-

HPO42- → H+ + PO4

-3

Combined:H2SO4 → 2H+ + SO4

2-

Combined: H3PO4 → 3H+ + PO4

3-


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For the following identify the acid and the base as strong or weak .

a. Al(OH)3 + HCl

b. Ba(OH)2 + HC2H3O2

c. KOH + H2SO4

d. NH3 + H2O

Weak base Strong acid

Weak acid

Strong acid

Strong base

Strong base

Weak baseWeak acid


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For the following predict the product. To check your answer left click on the mouse. Draw a mechanism detailing the proton movement.

a. Al(OH)3 + HCl

b. Ba(OH)2 + HC2H3O2

c. KOH + H2SO4

d. NH3 + H2O

AlCl3 + 3 H2O

Ba(C2H3O2)2 + 2 H2O

K2SO4 + 2 H2O

NH4+ + OH-

2

2

3

Reactions between acids and bases

When and acid and a base react with each other, the characteristic properties of both are destroyed. This is called neutralization.

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Reactions between acids and bases

General formula for acid base reaction:

Acid + Base → H2O +Salt

“Salt” means any ionic compound formed from an acid/base reaction

NOT JUST NaCl !!

Neutralization Reaction Animation

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Neutralization

HCl + NaOH → H2O + NaCl acid base water salt

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NeutralizationAnother Example

HNO3 + KOH → H2O + KNO3

H OHKNO3

acid base water salt

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Concentration

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Strength of an acid or base is determined by the amount of ionization. Concentration is determined by the amount of water added to the substance.

Molarity (M)

The number of moles of solute dissolved in each liter of solution.

Molarity = moles of solute

liters of solution

Example Problem #1

If 1.00 liter of sugar water contains exactly 1.00 mole of sugar, what is its molarity?Molarity = 1.00 mol

1.00 L

Molarity = 1.00 M

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Example Problem #2

If 1.00 liter of sugar water contains exactly 2.00 mole of sugar, what is its molarity?Molarity = 2.00 mol

1.00 L

Molarity = 2.00 M or 2.00 mol/L

(Twice as concentrated…)

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Example Problem #3

What is the molarity when 0.75 mol is dissolved in 2.50 L of solution?

Molarity = 0.75 mol = 0.30 mol/L or 0.30M

2.50 L

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In Lab, grams are typically used in place of moles.If you wanted to make 2.00L of a 6M HCl solution, how much HCl would you need?

First, calculate the molar mass of the acid.

H 1 x 1.00795 = 1.00795

Cl 1 x 35.453 = 35.453

36.46095 = 36.461

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If you wanted to make 2.00L of a 6M HCl solution, how much HCl would you need?

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First, calculate the molar mass of the acid.

HCl contains 36.461 g/mol

It would take 36.461 g of HCl to make 1 liter of a 1M HCl solution. How many grams would it take to make 2L of a 1M solution?

2 x 36.461g = 72.922g

If you wanted to make 2.00L of a 6M HCl solution, how much HCl would you need?

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It takes 72.922g of HCl to make 2 liters of a 1M solution. How much would it take to make 2 liters of a 6M solution?

6 x 72.922g = 437.532 g

Try One More

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Suppose you wanted to make 2 liters of a 0.5 M solution of HCl. How much HCl would you need?

Each mole of HCl is equal to 36.461gFor a 0.5 M solution, you would need

half that much. 36.461 x 0.5 = 18.2305g.

However, you want to make 2 liters, so double that amount. 18.2305 x 2 = 36.461g.

TITRATIONTITRATION

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Titration of a strong acid with a strong base

ENDPOINT = POINT OF NEUTRALIZATION = ENDPOINT = POINT OF NEUTRALIZATION = EQUIVALENCE POINTEQUIVALENCE POINT

At the end point for the titration of a strong acid with a strong base, the moles of acid (H+) equals the moles of base (OH-) to produce the neutral species water (H2O). If the mole ratio in the balanced chemical equation is 1:1 then the following equation can be used.

MOLES OF ACID = MOLES OF BASE

nnacidacid = n = nbasebase

Since M=n/V

MMAAVVAA = M = MBBVVBB

TITRATIONTITRATION

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MMAAVVAA = M = MBBVVBB

1. Suppose 75.00 mL of hydrochloric acid was required to neutralize 22.50 mLof 0.52 M NaOH. What is the molarity of the acid?

HCl + NaOH HCl + NaOH H H22O + NaClO + NaCl

MMaa V Vaa = M = Mbb V Vbb rearranges to M rearranges to Maa = M = Mbb V Vbb / V / Vaa

so Mso Maa = (0.52 M) (22.50 mL) / (75.00 mL) = (0.52 M) (22.50 mL) / (75.00 mL)

= 0.16 M= 0.16 M

Now you try:2. If 37.12 mL of 0.843 M HNO3 neutralized 40.50

mL of KOH, what is the molarity of the base?Mb = 0.773 mol/L

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Molarity and Titration

TITRATIONTITRATION

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Titration of a strong acid with a strong base

ENDPOINT = POINT OF NEUTRALIZATION ENDPOINT = POINT OF NEUTRALIZATION = EQUIVALENCE POINT= EQUIVALENCE POINT

At the end point for the titration of a strong acid with a strong base, the moles of acid (H+) equals the moles of base (OH-) to produce the neutral species water (H2O). If the mole ratio in the balanced chemical equation is NOT 1:1 then you must rely on the mole relationship and handle the problem like any other stoichiometry problem.

MOLES OF ACID = MOLES OF BASEMOLES OF ACID = MOLES OF BASE

nnacidacid = n = nbasebase

TITRATIONTITRATION

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1. If 37.12 mL of 0.543 M LiOH neutralized 40.50 mL of H2SO4, what is the molarity of the acid?

2 LiOH + H2 LiOH + H22SOSO44 Li Li22SOSO44 + 2 H + 2 H22OO

First calculate the moles of base:

0.03712 L LiOH (0.543 mol/1 L) = 0.0202 mol LiOH0.03712 L LiOH (0.543 mol/1 L) = 0.0202 mol LiOHNext calculate the moles of acid:

0.0202 mol LiOH (1 mol H0.0202 mol LiOH (1 mol H22SOSO4 4 / 2 mol LiOH)= 0.0101 / 2 mol LiOH)= 0.0101 mol Hmol H22SOSO44

Last calculate the Molarity::

MMa a = n/V = 0.010 mol H= n/V = 0.010 mol H22SOSO44 / 0.4050 L = 0.248 M / 0.4050 L = 0.248 M

2. If 20.42 mL of Ba(OH)2 solution was used to titrate29.26 mL of 0.430 M HCl, what is the molarity of the barium hydroxide solution?

Mb = 0.308 mol/L

pHpHA measure of the hydronium ionA measure of the hydronium ion

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The scale for measuring the hydronium ion concentration [H3O+] in any solution must be able to cover a large range. A logarithmic scale covers factors of 10. The “p” in pH stands for log.

A solution with a pH of 1 has [H3O+] of 0.1 mol/L or 10-1



pH = - log [HpH = - log [H33OO++]]

The pH scaleThe pH scale

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The pH scale ranges from 1 to 10The pH scale ranges from 1 to 10-14-14 mol/L or from 1 to 14.mol/L or from 1 to 14.

pH = - log [H3O+]

1 2 3 4 5 6 7 8 9 10 11 12 13 14

acidacid neutral neutral basebase

Manipulating pHManipulating pH

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Algebraic manipulation of:Algebraic manipulation of: pH = - log [H3O+]

allows for:allows for:[H3O+] = 10-pH

If pH is a measure of the hydronium If pH is a measure of the hydronium ion concentration then the same ion concentration then the same equations could be used to describe equations could be used to describe the hydroxide (base) concentration. the hydroxide (base) concentration.

[OH-] = 10-pOH pOH = - log [OH-]

thus:thus:pH + pOH = 14 ; the entire pH range!

PRACTICE PROBLEM #25

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1. How many milliliters of 1.25 M LiOH must be added to neutralize 34.7 mL of 0.389 M HNO3?

2. What mass of Sr(OH)2 will be required to neutralize 19.54 mL of 0.00850 M HBr solution?

3. How many mL of 0.998 M H2SO4 must be added to neutralize 47.9 mL of 1.233 M KOH?

4. What is the molar concentration of hydronium ion in a solution of pH 8.25?

5. What is the pH of a solution that has a molar concentration of hydronium ion of 9.15 x 10-5?

6. What is the pOH of a solution that has a molar concentration of hydronium ion of 8.55 x 10-10?

10.8 mL

0.0101 g

29.6 mL

5.623 x 10-9 M

pH = 4.0

pOH = 4.9

Molarity and Titration

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A student finds that 23.54 mL of a 0.122 M NaOH solution is required to titrate a 30.00-mL sample of hydr acid solution. What is the molarity of the acid?

A student finds that 37.80 mL of a 0.4052 M NaHCO3 solution is required to titrate a 20.00-mL sample of sulfuric acid solution. What is the molarity of the acid?

The reaction equation is:H2SO4 + 2 NaHCO3 → Na2SO4 + 2 H2O + 2 CO2

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Water Equilibrium

Water Equilibrium

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Kw = [H+] [OH-] = 1.0 x 10-14

Equilibrium constant for water

Water or water solutions in which [H+] = [OH-] = 10-7 M are neutral solutions.

A solution in which [H+] > [OH-] is acidic

A solution in which [H+] < [OH-] is basic

GROUP STUDY PROBLEM #25

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______1. How many milliliters of 0.75 M KOH must be added to neutralize 50.0 mL of 2.50 M HCl?

______2. What mass of Ca(OH)2 will be required to neutralize 100 mL of 0.170 M HCl solution?

______3. How many mL of 0.554 M H2SO4 must be added to neutralize 25.0 mL of 0.9855 M NaOH?

______ 4. What is the molar concentration of hydronium ion in a solution of pH 2.45?

______ 5. What is the pH of a solution that has a molar concentration of hydronium ion of 3.75 x 10-9?

______ 6. What is the pOH of a solution that has a molar concentration of hydronium ion of 4.99 x 10-4?

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KWISHA!

Kwisha!

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UESTIO

NS?

PROFESA WALTER WAKHUNGU

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Education

Final acid and bases rev