Acids, Alkalis and Salts

Question 1

Describe the method of salt solution preparation (using an insoluble solid and an acid)

Answer 1

• Warm approx. 20cm³ of acid in a boiling tube using a water bath
• Add acid into a beaker
• Gradually add insoluble solid to the acid and stir until it is in excess
• Use filter paper and a funnel to filter the contents of the beaker

Question 2

Describe the method of crystallisation

Answer 2

• Pour filtered solution of the salt solution in an evaporating basin
• Heat using a Bunsen burner (or leave for a week) until it is saturated - crystals form on glass rod when dipped in the salt solution
• Leave it in a cool place for at least 24hrs to let it cool down and crystallise
• Filter the remaining fluid from the crystals
• Gently pat dry the crystals

Question 3

General word equation
Metal + acid -> ?

Answer 3

Salt + hydrogen

Question 4

General word equation
Alkali + acid -> ?

Answer 4

Salt + water

Question 5

General word equation
Base + acid -> ?

Answer 5

Salt + water

Question 6

General word equation
Carbonate + acid -> ?

Answer 6

Water + carbon dioxide + salt

Question 7

General word equation
Ammonia + acid -> ?

Answer 7

Ammonium salt

Question 8

All acids contain ________ ions

Answer 8

Hydrogen (H+)

Question 9

All alkalis contain _________ ions

Answer 9

Hydroxide (OH-)

Question 10

Litmus in acids, neutrals and alkalis

Answer 10

Acid: red
Neutral: purple
Alkali: blue

Question 11

Phenolphthalein in acids, neutrals and alkalis

Answer 11

Acid: colourless
Neutral: colourless
Alkali: pink

Question 12

Methyl orange in acids, neutrals and alkalis

Answer 12

Acid: red
Neutral: orange
Alkali: yellow

Question 13

Universal indicator in acids, neutrals and alkalis

Answer 13

Acids: red
Neutral: green
Alkalis: blue/purple

Question 14

Acids are proton ______

Answer 14

Donors

Question 15

Bases are proton _________

Answer 15

Acceptors

Question 16

Neutralisation (give equation)

Answer 16

When an acid reacts with an alkali it produces a salt and water
H+ (aq) + OH- (aq) -> H2O (l).

Question 17

SPA (Sodium, Potassium, Ammonium) salts are all…

Answer 17

Soluble

Question 18

All nitrates are…

Answer 18

Soluble

Question 19

All chlorides are _______ except…

Answer 19

Soluble, except silver chloride and lead II chloride

Question 20

All sulfates are _______ except…

Answer 20

Soluble, except calcium sulfate, barium sulfate and lead II sulfate

Question 21

All hydroxides are _________ except… (what is special about a certain hydroxide?)

Answer 21

Insoluble except SPA salts and calcium hydroxide is slightly soluble

Question 22

All carbonates are _________ except

Answer 22

Insoluble, except SPA salts

Question 23

Titration (soluble salt)

Answer 23

• Use a pipette to transfer exactly 25cm3 of an alkali to a conical flask
• Add 3 drops of methyl orange indicator to the conical flask
• Fill the burette with acid and ensure that there are no air bubbles
• Run a little acid out into a beaker to fill the jet
• Record initial volume of acid in the burette
• Add acid to the alkali in the conical flask, swirling the conical flask all the time
• As the indicator begins to change colour, add the acid dropwise until there is a permanent colour change
• Record final volume of acid in burette
• Repeat titration until 2 results are condordant (within 0.20cm3)
• Repeat without indicator, adding mean value of acid to obtain a pure salt for crystallisation

Question 24

Precipitation (insoluble salt)

Answer 24

• Mix 2 solutions
• Filter precipitate
• Wash with distilled water
• Dry (no need for crystallisation)

Question 25

Crystallisation

Answer 25

• Pour solution into an evaporating basin
• Heat basin gently until a saturated solution is formed (dip glass rod into solution to see if crystals form)
• Stop heating and allow solution to cool to form large crystals
• Filter remaining liquid after and blot dry