Acids, Alkali, Bases and salt preperation

Question 1

Red litmus (from acid to alkali)
Blue litmus
Phenolphthalein
Methyl orange

Answer 1

Red, Red, Blue
Red, Blue, Blue REMEMBER IT ONLY CHANGES THE MIDDLE
Colourless, Colourless, Pink
Red/orange, yellow, yellow

Question 2

Why is universal indicator used to measure the approximate pH value of an aqueous solution

Answer 2

It operates across a broad pH range and is useful for estimating the pH of an unknown solution

Question 3

Why do acids neutralize alkali and vice versa

Answer 3

Presence of H+ ions make a solution acidic, and OH- ions make an aqueous solution alkali
Neutralisation - H+ OH- becomes H2O

Question 4

Sodium, potassium and ammonium

Answer 4

Soluble

Question 5

All nitrates

Answer 5

Soluble

Question 6

Chlorides

Answer 6

Soluble (except Silver chloride and Lead(II) chloride

Question 7

Sulfates

Answer 7

Soluble (except Barium sulfate, calcium sulfate and lead(II) sulfate

Question 8

Carbonates

Answer 8

Insoluble (except sodium, potassium and ammonium carbonates)

Question 9

Hydroxides

Answer 9

Insoluble (except sodium, potassium and calcium hydroxides [calcium hydroxide is slightly soluble])

Question 10

Alkali + acid ->

Answer 10

salt + water

Question 11

base + acid ->
metal oxides and hydroxides are bases

Answer 11

salt + water

Question 12

metal + acid ->

Answer 12

salt + hydrogen

Question 12

carbonate + acid ->

Answer 12

salt + carbon dioxide + water

Question 13

metal + water ->

Answer 13

metal hydroxide + hydrogen

Question 14

metal oxide + water ->

Answer 14

metal hydroxide BALANCE IT

Question 15

Ammonia + water ->

Answer 15

NH4+ (aq) + OH-

Question 16

Titration method (example sodium hydroxide + water)

Answer 16

1. Pipette 25cm^3 of alkali (NaOH) into a conical flask
2. Add indicator
3. Titrate the acid through the burette in small portions and swirl, until there is a sharp color change
4. Quickly close the tap and record the volume (eye level with meniscus)
5. Repeat the experiment without indicator given the volume of acid needed (no impurities)
6. Transfer to evaporating basin and heat the solution, and allow it to cool so that crystals form (remove H2O, saturate salt)
7. Dry by leaving in a warm place

Question 17

Precipitation method (example forming silver chloride)

Answer 17

silver nitrate + potassium chloride (two soluble salt solutions) -> silver chloride(s) + potassium nitrate(aq) one sol. one insol.
1. mix the two salt solutions together in a beaker
2. stir with a glass rod (ensure all reactants have reacted)
3. filter the insoluble salt using filter paper and funnel
4. wash the insoluble salt with distilled water (to remove all of the remaining soluble salt)
5. Dry by leaving in a warm place

Question 18

Neutralisation/Excess Solid method (example forming copper(II)sulfate from copper(II) oxide)

Answer 18

CuO + H2SO4 -> copper sulfate + water
1. Heat acid in a beaker (speed up reaction)
2. Add base (CuO) in excess (until no more CuO dissolves) and stir with glass rod
3. Filter the mixture using filter paper and funnel
4. Gently heat the filtered solution until crystals form (check if they form on end of a glass rod to show saturated solution)
5. Dry by leaving in a warm place

Question 19

When to use titration:

Answer 19

Soluble, sodium or potassium salt

Question 20

When to use precipitation:

Answer 20

Insoluble salt

Question 21

When to use neutralisation:

Answer 21

Soluble, not sodium or potassium salt