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What happens to acids and alkalis when dissolved in water? (in aqueous solution)
Acids break down and release H+ ions
Alkalis break down and release OH- ions
What is a concentrated acid?
an acid with a lot of acid and little water per set volume
What is a dilute acid?
An acid with a lot of water and little acid per unit volume
What is a strong acid?
An acid that ionises completely in water and fully breakdowns into it’s ions
The greater the number of H+ ions released, the stronger the acid
Examples of strong acids
Hydrochloric acid, nitric acid, sulfuric acid, phosphoric acid
What is a weak acid?
An acid that only partially ionises in water
Examples of weak acids
Carboxylic acids such as ethanoic acid
Hydrochloric acid
HCl (aq)
Nitric acid
HNO3 (aq)
Sulfuric acid
H2SO4 (aq)
Phosphoric acid
H3PO4 (aq)
What is pH?
A logarithmic scale based on the concentration of H+ (aq) ions
Table of concentration of H+ (aq) ions in mol/dm³ and pH value
1.0 × 10^-1 = 1.0
1.0 × 10^-2 = 2.0
1.0 × 10^-3 = 3.0
1.0 × 10^-4 = 4.0
What happens to the pH when the acid is stronger?
There are more H+ (aq) ions in the solution so there is a lower pH
Describe colours of solution in relation to their pH when universal indicator is added
0 - red, 1 - dark orange, 2 - orange, 3 - yellow, 4-8 green, 9 - turquoise, 10 - pale blue, 11-12 dark blue, 13-14 purple
Colours for methyl red indicator
In acid = red, in alkali = yellow
Colours for phenolphthalein indicator
in acid = colourless, in alkali = pink
Acid + metal →
Salt + hydrogen
Acid + metal oxide →
salt + water
acid + alkali (metal hydroxide) →
salt + water
acid + metal carbonate →
salt + water + carbon dioxide
ammonia + acid →
ammonium acid
hydrochloric acid →
… chloride salts
Nitric acid →
… nitrate salts
Sulfuric acid →
… sulphate salts
Neutralisation reaction
acid + base → salt + water
Ionic equation for a neutralisation reaction between an acid and an alkali
H+(aq) + OH-(aq) → H20(l)
What indicators should you use for titration and why?
Indicators that only have one colour change (NOT universal indicator)
What is the end-point?
The pH at which the indicator changes colour
Soluble meaning
Able to dissolve in water
Saturated meaning
high concentrated of solute dissolved in solvent
Concordant results
results that are within 0.10 cm³ of each other
ammonium ion
NH4+
nitrate ion
NO3-
hydroxide ion
OH-
sulphate ion
SO4 2-
carbonate ion
CO3 2-
