Chemistry acid and bases

Acids

A proton donator

Acids properties

-sour

-ph less that 7 (1 is strongest, 6 is weakest)

-turn blue litmus paper red

Weak acids

Partially ionises in water to give H+ ions. ethanoic acid CH3COOH

Strong acids

Ionises fully in water to give H+ protons . Hcl (hydrochloric acid) H2SO4 ( sulfuric acid), HNO3 (nitric acid)

Monoprotic acids

Donate one proton per molecule in water

Diprotic acids

Donate 2 protons per molecule in water

Acid + base =

Salt and water . This reaction is also called neutralisation

Acid + carbonate

Salt + water + carbon dioxide

To test for carbon dioxide

Limewater is used. A white precipitate will be formed in limewater

Acid + metal

Salt + hydrogen gas

to test for hydrogen

Lighted splint test . Splint will extinguish and a pop sound would be heard

Bases

Metal oxides or a metal hydroxide that reacts with acid to form a salt and water only

Alkalis

Soluble base which dissolves to produce hydroxide ions in aqueous solution

Strong alkalis

Potassium hydroxide, calcium hydroxide, sodium hydroxide

Weak alkalis

NH3(ammonia)

Properties of alkali

-turn red litmus paper blue

-bitter

Ph scale

1-6: acids (strongest acid is 1 , weakest acid is 6)

7: pure water

8-14 ( 8 is least basic , 14 is most basic

How can ph be measured

Universal indicator, litmus paper, phenolphthalein, methyl orange

Universal indicator

0-2: red

3-4: orange

4-6:yellow

7:pale green

8-11: green-blue

12-14: violet

Litmus

Turns red when reacting with acid

Turns blue when reacting with alkali

Phenolphthalein

Acidic : colourless

Neutral : colourless

Alkaline : pink

Methyl orange

Ph less than 3.5: red

Neutral :yellow

Alkaline: yellow

Oxides

A compound of oxygen and another element

Basic oxides

Metal burns in oxygen

Acidic oxides

A non metal burns in oxygen

Salt

Ionic compound formed by reacting acids with metals carbonates bases or alkalis

Cations

Positive ions

Anions

Negative ions

Soluble salts

SODIUM,POTASSIUM, AMMONIUM (group1)

NITRATE

InSoluble chlorides

• Most are soluble except lead chloride and silver chloride

Insoluble sulfates

Calcium sulfate, lead sulfate, barium sulfate, rest is soluble

Soluble carbonate/oxides/hydroxides

-mostly insoluble except sodium carbonate , potassium carbonate and ammonium carbonate +group 1 salts

Titration

• Salt preparation

• For soluble salts

• Sodium potassium and ammonium salts

• Acid+alkali (eg.the soluble salt __ can be prepared by titrating (acid) against (alkali)

Precipitation

• soluble +soluble

• Preparation of insoluble salt (eg.the insoluble salt can be prepared by mixing solutions of (soluble salt that’s aq)and (soluble salt that’s aq)

MCO

• non spa salts that are soluble

• Acid with metal carbonate and oxide

• Eg. the soluble salt can be prepared by reacting base/metal oxide (insoluble)with soluble acid

Precipitation procedure

1. Add aqueous (soluble salt) to (soluble salt), eg. barium nitrate+sodium sulfate

2. Filter to remove the precipitate( a solid that settles out of a liquid solution)formed , eg. barium sulfate

3. Barium surface is the residue ( left on filter paper)

4. Wash the precipitate with distilled water to remove soluble impurities

5. Dry the precipitate between filter paper or heat the precipitate to dry it

Titration preparation

1. Pipette(used to measure liquid) a fixed volume of acid into a conical flask eg. Hcl

2. Add a few drops of suitable indicator eg. methyl orange (helps to see when neutralisation occurs )

3. Titrate with potassium hydroxide from a burette until the indicator shows the solution is neutral (end point).

   4. Stop the titration and record the volume of potassium hydroxide added.

   5. Repeat without indicator by asking the recorded volume of potassium hydroxide .

   6. Evaporate the water from the salt solution to get solid potassium chloride crystals.

MCO preparation

1. Add excess insoluble oxide to the soluble acid in a beaker and warm eg. add copper 2 oxide to dilute sulfuric acid

2. Filter to remove the unreacted excess copper 2 oxide

3. Heat the solution to evaporate most water from solution until it’s saturated

4. Cool the solution to firm blur crystals of copper 2 sulfate

5. Filter the mixture to remove the crystals

6. Wash and dry the crystals between filter paper