Arhenius theory:

Acid:

An acid is a substance which releases H⁺ _(aq) in water.

Example:

HCl_(aq) à H⁺ _(aq) + Cl^-_(aq)

Study Clue: An acid is an ionic specie whose formula starts with an "H" e.g HCN, HCl.

Base:

A base is any substance which releases OH^-

Example:

NaOH_(aq) à Na⁺ _(aq) + OH^-_(aq)

Study Clue: A base is an ionic specie whose formula ends with OH^-_(aq) e.g  KOH, NaOH

Salt:

A neutarlization product which results when a n acid and base react.

Example: NaCl, KCl

Study Clue: salt is an ionic compound which is neither an acid or a base.

Porperties:

Properties of Acid:

• ancid react with base.
• acids are electrolye
• acid act on some metals to produce H_{2 (g)}
•  litmus paper is RED in ACID
• Tastes sour.

 Properties of Base:

• Base react with acid.
• bases are electrolyte.
• bases feel slippery.
• Litmus paper is BLUE in BASE.

Note:

H⁺  is called proton.

H₃O⁺is called hydronium ion.

Bronsted Lowry theory:

Acid:

It is a substance which donates a proton to another substance. (an acid is a proton (H⁺) donor)

Example: HCl_(aq) + à H₃O⁺ + Cl^-

Base:

It is a substance which accepts a proton from another substance.

Example: NH₃ + H₂ O à NH₄⁺ + OH^-

Amphiprotic:

A substance which can either act as an acid or base.

Example:

           + H⁺     - H⁺

H₃PO₄ßH₂PO₄àHPO₄^-

Study clue:

If a substance possesses a negative charge and still has an easily removable hydrogen then the substance will be amphiprotic.

Note:

strong acid and bases ionizes 100%.

NaOH à Na⁺ + OH^-

HCl à H⁺ + OH^-

Equilibrium occurs only in weak acid and bases not in strong acid and bases

A weak acid or a base ionizes less than 100%.

Strong acids:

Leveling Effect:

The term describing the fact that all strong acids are 100% ionized and are to the solution of H₃O⁺ while all strong bases are 100% dissociated in aqueous solution to solution of OH^-

H₃O⁺ßà H⁺ + H₂O

Nentral solution [H₃O⁺]=[OH^-]

Acidic solution [H₃O⁺] >[OH^-]

Basic solution [H₃O⁺]<[OH^-]

K_w= [H₃O⁺][OH^-]

K_w= 1.0 * 10^-14 at 25^oC unless you are told otherwise

K_a: is an acid ionization constant

C H₃COOH + H₂Oßà C H₃COO^- + H₃O⁺

K_a= [C H₃COO^-][H₃O⁺]/[C H₃COOH]

K_b: is a base ionization constant

NH₃+ H₂Oßà NH₄⁺ + OH^-

K_b= [NH₄⁺][OH^-]/[NH₃]

Conjugate pair = K_a(Conjugate) * K_b(Conjugate)

In a Bronsted-Lowry acid base equilibrium, the side of the equilibrium which has the weaker acid will be favoured.

Equilibrium occurs only in weak acid and bases not in strong acid and bases

strong bases are mostly alkaline metal hydroxide.

H₃O⁺ßà H⁺ + H₂O

C H₃COOH + H₂Oßà CH₃COO^- + H₃O⁺

Expression for calculating equilibrium is

K_eq = K_a (reactant acid)/K_a (product acid)

pH = -log [H₃O⁺]

pOH = -log[OH^-]

Note:

• pH scale increases as the pOH scale decrease
• acidic solution is less than 7. basic solution pOH less than 7. pH is greater than 7 in basic solution. Neutral solution has pH=pOH=7.

Hydrolysis:

The hydrolysis of salt is a reaction under water and the cation or anion (or both) contained in the salt so as to produce an acidic or basic solution.

Note: All salt are considered to be 100% ionized water.

Example: NH₄Cl à NH₄ + Cl^- à NH₄⁺ + H₂OßàNH₃ + H₃O⁺

Spectators:

The conjugates of strong acids and passes are spectator ions.

Ions that don’t precipitate in reaction.

Example:

NaOH à Na⁺ + OH^-

Na⁺ can’t reform NaOH in an equilibrium (NaOH ionizes 100%) so that a reaction between Na⁺ and H₂O can’t occur.

Spectator cation will be the alkali metals and its ions.

Spectator anions found at the top right of table relative strength.

For amphiprotic ions K_eq is compared for its acid and base form and which ever K_eq is bigger its going to act according.

Titration:

A titration is a process in which a measured amount of a solution is reacted with known volume of another solution. Until a desired equivalence point is reached.

Example:  NaOH + HCl à NaCl + H₂O

Note:

The equivalence point occurs when the mole ratio in the reaction exactly equals the mole ratio required by the stoichiometry of the reaction.

C =n/v

Where               c = molar concentration

                        n = moles in solution

                        v = volume of solution.

All titration problems involve at least five titrations.

Concentration of acid

Volume of acid

Concentration of base

Volume of base

Base/acid mole ratio

Partial neutralization:

One mole of polyprotic acid molecule H₂SO₄ has 2 mol of removable protons.

H₂SO₄ + OH^- à HSO₄^- + H₂O

H₂SO₄ + 2OH^-à SO₄^2- + 2H₂O

Percentage purity:

Percentage purity: = Actual concentration / Expected Concentration * 100%

Indicator:

An indicator is a weak organic acid or base with different colors of its acid and base forms

Example:

HIn + H₂O ßà In^-  + H₃O⁺

Yellow                red

Note:

• In acidic solution [HIn] > [In^-]
• In basic solution [In^-] > [HIn]
• [HIn]=[In^-] is called transition point. The point at which an indicator is halfway through its color change.
• At the endpoint
• K_a = [In^-][ H₂O]/[HIn] = [H₃O⁺]       (since [HIn] = [In^-])
• Universal indicator:
• An indicator solution which changes color several times or a range of pH values.

Note:

A universal indicator solution is made up by mixing the following indicators:

• Methyl orange
• Bromothymol blue
• Phenolthalein

Standard solution:

A solution with an accurate known concentration.

Example:

NaOH + HCl à NaCl + H₂O

15ml       25 ml

0.1M     ?

NaOH is standard solution

Primary standard solution:

A substance which can be obtained in pure and stable form, which doesn’t absorb H₂O

 Or CO₂ from the air and which has a known molar mass such that it can be used to prepare a solution of known [ ].

Example:

Acidic primary standard:KHC₈H₄O₄ and H₂C₂O₄. 2H₂O

Basic primary standard: Na₂CO₃

Types of titration curve:

Strong acid with strong base:

V_B is the volume of base required to reach equivalence point.

The salt of strong acid and strong base is neutral.

Example: NaOH + HCl à NaCl + H₂O

Weak acid with Strong Base:

V_B is the volume of base required to reach equivalence point is and V_1/2 = ½ V_B that V_1/2 is the point on the graph which is half the value of V_B.

The equivalence point occur above pH = 7

The value of K_a can be found from the equation.

 K_a = [H₃O⁺]_1/2 where [H₃O⁺] is found from pH_1/2

The molarity of weak acid can be found from the equation

[HA] = [H₃O⁺]/ K_a

Where [H₃O⁺] is from pH_init

Weak base with Strong Acid:

The pH equivalence point is less than 7

The value of K_b can be found from the equation.

Kb = [OH^-] _½  where [OH^-] is found by converting pH_1/2 to pOH_1/2 and then [OH^-]_1/2

The molarity can be found from equation.

[B-} = [OH-]/Kb

Where [OH^-] is from the pH _init

Study clue:

Salt of STRONG ACID and STRONG BASE is NEUTRAL.

The salt of a STRONG ACID and a weak base is ACIDIC.

The salt of weak acid and STRONG BASE is BASIC.

Buffers:

Solution which contains sufficient amount of weak acid and its conjugate weak base. It resists pH change.

Example:

Acidic buffer: CH₃COOH +H₂O ßà CH₃COO^- +H₃O⁺

Basic buffer: NH₄⁺ + H₂OßàNH₃ + H₃O⁺

Note:

When equal [ ] of weak acid and its conjugate base are added to water the pH of the resulting buffer will equal the pK_a value of the weak acid

Diluting buffer has no effects on its pH.

Whenever a weak acid or base is titrated, a buffer solution will occur in the middle portion of titration curve.

Buffer in biological system:

The main buffer solution in blood is CO₂ and HCO₃^-

H2PO4 and HPO4- are present in smaller extent.

Metal Oxides:

Ionic metal oxides form basic solution.

Example:

Na2O + H₂O ß à 2NaOH

Non metal oxide:

Nonmetal oxide react with water to form acidic solution.

Example:

SO₃ + H₂O à H₂SO₄

Acid rain:

CO₂ naturally dissolve in water causing the pH to be about 5.6

H₂O + CO₂  ßà HCO₃^- + H₃O⁺

Any precipitation < 5.6 is acid rain.

Source of acidity:

Most fuels such as coal and oil give off SO₂ which react with water producing H₂SO₄ .

Combustion reaction in an automobile cause small amount of N₂ to react with oxygen in air producing NO₂ which react with water vapor producing HNO₂ and HNO₃

Natural protection:

Lime stones neutralize the acidity of acid rain.