iGCSE Edexcel Chemistry Inorganic Part 2

when acids are added to water...

they form positively charged hydrogen ions (H⁺)

describe the method of performing a titration

Use the pipette and pipette filler and place exactly 25 cm3 sodium hydroxide solution into the conical flask

Place the conical flask on a white tile so the tip of the burette is inside the flask

Add a few drops of a suitable indicator to the solution in the conical flask

Perform a rough titration by taking the burette reading and running in the solution in 1 - 3 cm3 portions, while swirling the flask vigorously

Quickly close the tap when the end-point is reached (sharp colour change) and record the volume, placing your eye level with the meniscus

Now repeat the titration with a fresh batch of sodium hydroxide

As the rough end-point volume is approached, add the solution from the burette one drop at a time until the indicator just changes colour

Record the volume to the nearest 0.05 cm3

Repeat until you achieve two concordant results (two results that are within 0.1 cm3 of each other) to increase accuracy

acidic

pH below 7

basic

pH greater than 7

litmus

red in acid, blue in alkali

phenolpthalein

colorless in acid, pink in alkali

methyl orange

red in acid, yellow in alkali

neutralisation

when an acid reacts with an alkali

titrations

method of analysing the concentration of solutions

universal indicator

a wide range indicator and can give only an approximate value for pH

when alkalis are added to water...

they form negative hydroxide ions (OH⁻)

acid + base ->

salt + water

test for ammonia gas

damp red litmus paper turns blue

test for carbon dioxide gas

bubble through lime water; lime water turns milky/cloudy

test for chlorine gas

damp blue litmus paper is bleached

test for hydrogen gas

hold a lighted splint in mouth of test tube; burns with a 'squeaky pop' sound

test for oxygen gas

hold a glowing splint; splint relights

flame test result for lithium

red

flame test result for sodium

yellow

flame test result for potassium

lilac

flame test result for calcium

orange-red

flame test result for copper

blue-green

describe the method of flame tests

Dip the loop of the wire in dilute hcl

hold it in the blue flame

Dip the loop of the wire in the sample

place loop back into the blue flame

result of hydroxide test for ammonium

ammonia gas produced turns damp red litmus blue

result of hydroxide test for copper (II)

light blue precipitate formed

result of hydroxide test for iron (II)

green precipitate formed

result of hydroxide test for iron (III)

red-brown precipitate formed

how are metal cations identified in aqueous solution?

the colour of the precipitate formed on addition of NaOH

result of halide test for chloride

white precipitate formed

result of halide test for bromide

cream precipitate formed

result of halide test for iodide

yellow precipitate formed

result of sulphate test for sulphate

white precipitate formed

result of carbonates test for carbonate

effervescence, gas produced is CO2 which turns limewater mily

carbonate test

add dilute acid and test the gas released

sulphate test

acidify with dilute niric acid and add aqueous barium nitrate

halide test

acidify with dilute niric acid and add aqueous silver nitrate

chemical test for water

anhydrous copper(II) sulfate turns from white to blue on the addition of water

physical test for water

aphysical test to see if a sample of water is pure is to check its boiling point

A sample of the liquid is placed in a suitable container such as a boiling tube and gently heated

Using a thermometer, you can check if the boiling point is exactly 100 oC

Any impurities present will usually tend to raise the boiling point and depress the melting point of pure substa

acid + metal ->

salt + hydrogen

acid + metal carbonate ->

salt + water + carbon dioxide

SPAN

sodium, potassium, ammonium and nitrate

bases examples

usually oxides, hydroxides or carbonates of metals; ammonia is an usual base

solubility rules

-SPAN compounds are soluble

-chlorides are soluble, except silver + lead (II)

-sulphates are soluble except for those of barium, calcium + lead (III)

-carbonates are insoluble

-hydroxides are insoluble

strong acids

dissociate completely in water

weak acids

partially dissociate in water

formula linking moles, concentration and volume

moles(mol)=concentration(mol/dm^3)*volume(dm^3)

formula linking moles, mass and RFM

moles(mol)=mass(g)/RFM

dm^3=xcm^3

1000cm^3

acids are proton...

donors

bases are proton...

acceptors

how to prepare a soluble salt

reaction of an acid with an insoluble salt

how to prepare an insoluble salt

two soluble salts