A cid

Strong acid Acid that completely ionise in water to produce H+ Exp: HCl, H2SO4

Di roti roticc

Substance produced hydrogen 1 mol H+ ions when ionise in water. Example: HCl H+ + Cl-

 

 

Taste sour Turn blue limus paper to red pH < 7 conduct electricity

Tri Tri rot rotic

Substance produced hydrogen 2 mol H+ ions when ionise in water. Example:

Substance produced hydrogen 3 mol H+ ions when ionise in water. Example:

2H+ + SO42-

H2SO4

H+ CH3COOH CH3COOCH3COOH CH3COOH H+ CH3COOCH3COOH

3H+ + PO43-

H3PO4

Chemic Chemical al Pro erties erties A cid+ Alkali

Acid + metal oxide

salt + H 2  2 O 

MgSO4 + H2O

Asid + reactive metal

HCl + Mg

HCl + CaCO3

Salt + H 2  2 

MgCl2 + H2 Salt + CO 2  2  + H  2  2 O 

CaCl2 + CO2 + H2O

Base Strong alkali

Alkali that can ionize completely in water to form high concentration of hydroxide ion, OHExample: NaOH, KOH

Sulphuric acid  Making electrolyte in car battery Methanoic acid  Coagulate of latex Ethanoic acid  Food preservatives Carbonic acid  Making soft drink

Na2(SO4) + H2O

H2SO4 + NaOH

HCl + ZnO

Uses of acid

salt + H 2  2O   

Acid + metal carbonate 

KOH

Acid that partially ionise in water to produce H+ Exp: CH3COOH

Substance that dissociates in water to produce hydrogen ion, H+

Monno rot Mo rotic

Properties of acid

Weak

Acid

Dissolve in water

Chemical compound that react with acid to form salt and water only

Weak alkali

Alkali that can ionize partially in water to produces low concentration of hydroxide ion, OHExample: ammonia, NH3

Alkali Substance that dissociates in water to produce hydroxide ion, OH+

NH3

K+ + OH-

NH4+ + OH-

Uses of alkali Properties of alkali 



 

Taste bitter and slippery Turns red limus paper to blue pH > 7 conduct electricity

Sodium hydroxide Making soap/detergent  Magnesium hydroxide  Making toothpaste Calcium hydroxide  Making cement Ammonia  Prevent coagulation of latex

Chemical Properties

Alkali + Acid H2SO4 + NaOH

salt + H2O Na2(SO4) + H2O

Alkali + ammonium salt salt + H2O + NH3 NaOH + NH4Cl NaCl + H2O + NH3

H2O water help acid ionize to produced H+ ions

Role of water in acid

Without water/in organic solvent/glacial acid

With water

does not show acid properties acids remain in the form of molecules no free mobile hydrogen ions no acid properties HCl

→

There are no free H+ ions

HCl

HCl

Molecules in acids will ionise to hydrogen ions HCl(aq) H+ + ClThe presence of hydrogen ions are the causes the show acidic properties Has free mobile hydrogen ions

There are free H+ ions

H+

H+ Cl-

HCl

H+

Cl-

H2O water help alkali ionize to produced OH- ions

Role of water in alkali

Without water/in organic solvent/glacial acid does not show alkaline properties Alkali remain in- the form of . molecules no free mobile hydroxide ions No conduct electricity

NaOH

NaOH

NaOH

NaOH

With water Molecules in alkali will ionise to form hydroxide ions NaOH(aq) Na+ + OHThe presence of hydroxide ions are the causes the show alkaline properties Has free mobile hydroxide ions →

There are no free OHions

There are free OHions

Na+

Na+ -

OH

Na+

OH-

Concentration of H+

Concentration of OH-

Why At same concentration, the pH value of a weak acid lower than strong acid?  Because the concentration of OH- ions weak weak alkali is lower.  Weak alkali ionises partially but a strong alkali ionizes completely.

pH Scale

Strong acid: pH 1 -2 Weak acid : pH 3-6

Strong alkali pH 13 -14 Weak alkali : pH 8-12

X Mr

Concentration in g dm-3

-3

Concentration in mole dm (M)

pipette

÷ Mr No. of mole of solute

=

Molarity (M) = Volume of solution ( dm3)

Mass (g) Volume of solution(dm3)

n = MV 1000

M1 V1= M2 V2 Preparation standard solution

1 Weigh the mass of sodium hydroxide the solid sodium hydroxides into 2 Transfer beaker contain distilled water and stirred 3

Solution from beaker poured into volumetric flask

Rinsed beaker and filter funnel into i nto 4 volumetric flask

M1 – Molarity before dilution V1 – Volume before dilution M2 – Molarity after dilution V2 – Volume after dilution

Neutralization

-reaction accur between acid and base to form salt and water In neutralization , hydrogen ion in acid react with hydroxide ion from alkali. H+ + OH H2O

5 Add distilled water until graduation mark 6 Shake the volumetric flask

Example 1: 3.25 g of zinc, Zn reacted completely with hydrochloric acid, HCl with molarity of 0.5 mol dm-3.Calculate volume of acid used. (RAM Zn = 65)

Step 1

Zn + 2HCl -3 3.25 g 0.5 moldm

ZnCl2 + H2

Step 2

No. mole: 3.25/65 = 0.05

Step 3

Zn : HCl Ratio mole 1 : 2 No.of mole 0.05 0.05 x 2 = 1

Step 4

Molarity, M = no.of mole Volume (dm-3) Volume : 0.1 / 0.5 = 0.2 dm3 / 200 cm3

 Application of neutralization Slake lime – reduced soil acidity   Toothpaste – Mg(OH) 2 neutralise acid in mouth Baking powder – cure bee sting  Magnesium hydroxide – treat gastric pain

 D   i    l    u  t   i    o  n 

Hydrochloric acid

Potassium hydroxide solution + phenolphthalein

End Point – when all hydrogen ions from acid react completely with hydroxide ions from alkali to form water. Indicator Phenolphtalein Methyl orange

Colour in alkali Pink Yellow

Colour ion neutral Colourless orange

Colour in acid Colourless Red

Example 2: What is the volume of 1.0 moldm-3 sodium hydroxide solution which can neutralize 25 cm3 of 1.0 moldm-3 sulphuric acid

Step 1

H2SO4 + 2NaOH -3 -3 1.0 moldm 1.0 moldm 3 Volume? 25 cm

Step 2

No. mole: 3.25/65 = 0.05

Step 3

H2SO4 Ratio mole 1 No.of mole 0.025

Step 4

Molarity, M = no.of mole Volume (dm-3) Volume : 0.5 / 1.0 = 0.5 dm3 / 500 cm3

: :

Na 2SO4 + H2O

NaOH 2 0.025 x 2 = 0.5