Chemistry - Acids, salts and bases

acid + metal

salt + hydrogen

acid + metal oxide

salt + water

acid + metal hydroxide

salt + water

acid + metal carbonate

Salt + water + carbon dioxide

what is an acid

proton donors, releases H⁺ ions when dissolved in water

what is a base

proton acceptors, release OH^- when dissolved in water

what is an alkali

a base that is soluble in water

what colour is litmus for acidic - neutral - base

red - purple - blue

what colour is Phenolphthalein for acidic - neutral - base

colourless - pale pink - red

what colour is Methyl orange for acidic - neutral - base

red - orange - yellow

strong vs weak acids

strong acids fully dissociate in water producing H⁺ ions while weak acids only partially dissociate forming an equilibrium 

what 3 salts are all soluble

sodium, potassium, ammonium

what salt is always soluble

nitrates

common carbonates are..

insoluble , excluding sodium, potassium and ammonium

common chlorides are…

soluble, except silver and lead (||)

common sulphates are…

soluble, except barium, calcium and lead (||)

common hydroxides are…

insoluble, except sodium, potassium and calcium ( sparingly soluble )

hydrochloric acid

HCl

sulphuric acid

H₂SO₄

Nitric acid

HNO₃

Phosphoric acid

H₃PO₄

sodium hydroxide

NaOH

potassium hydroxide

KOH

Magnesium Hydroxide

Mg(OH)₂

Ammonium hydroxide

NH₄OH

colour of copper (||) oxide

Black

colour of sulphuric acid

colourless/ clear

copper (||) sulphate colour

Blue

why is the ( Sulphuric ) acid heated

To ensure that the reaction happens at a faster rate due to particles having more kinetic energy

why is it dangerous to heat the acid to a boiling point before adding the base

it can make the acid explode ( in your face)

how do we know all the acid is neutralised - insoluble base

(black) residue is formed

what does saturated mean

when no more solid/ solute can dissolve

how do you know when the salt solution e.g. copper(||) sulphate solution, was becoming saturated

there was an excess of black copper oxide at the bottom

explain how to make a pure dry salt using an acid and insoluble base

• measure out 40cm³ of the acid

• heat up the acid gently till it reaches about 60^oC

• add small amounts of the base ( metal carbonate or oxide ) until there is an excess residue at the bottom

• allow the solution to cool before filtering

• pour the filtrate into an evaporating basin, then heat this to evaporate some water. Once 50% of the water has evaporated stop heating

• Allow the remaining water to evaporate naturally

silver nitrate

AgNO₃

Ammonia

NH₄OH

what method do you use for an insoluble base

• heat acid gently….

what method do you use for an insoluble salt

precipitation

what method do you use for soluble bases

titration

Titration method - end point

Soluble salt by acid + alkali e.g. NaOH + H₂SO₄

• Measure out 25cm³ of NaOH using a pipette, that has been rinsed through with distilled water

• Transfer the NaOH into a conical flask and then add 3 drops of methyl orange

• Fill out a burette, that has been rinsed with distilled water, with H₂SO₄ and note the original volume

• Run the H₂SO₄ into the NaOH until it turns a pale orange

• note the final/end volume of the H₂SO₄ Then rinse out the conical flask and repeat the experiment until you have 2 results that are concordant

Titration method - pure, dry crystals

Soluble salt by acid + alkali e.g. NaOH + H₂SO₄

• Measure out 25cm³ of NaOH using a pipette, that has been rinsed through with distilled water

• Transfer the NaOH into a conical flask and then add 3 drops of methyl orange

• Fill out a burette, that has been rinsed with distilled water, with H₂SO₄ and note the original volume

• Run the H₂SO₄ into the NaOH until it turns a pale orange

• note the final/end volume of the H₂SO₄ . Then repeat without the indicator

• Heat the solution to saturate it and leave it to cool and crystallise before filtering

• pat dry with filter paper

Precipitation method - insoluble salt

e.g. Lead nitrate and sodium sulphate

• measure 25ml of 1moldm^-3 of lead nitrate solution and the same of sodium sulphate solution

• mix the 2 soluble salts by pouring into a 100ml beaker

• pour the mixture through a filter

• once all the filtrate has run through rinse the residue with distilled water

• place the lead (||) sulphate on a watch glass and leave in a warm place to dryne

how do you make an insoluble salt

two soluble salts, that contain the desired ions are measured and mixed to form an insoluble salt