acids

Question 1

what are acids in solution sources of

Answer 1

hydrogen ions

Question 2

what are alkalis in solution sources of

Answer 2

hydroxide ions

Question 3

recall the pH of acidic, alkaline and neutral solutions

Answer 3

• acidic = lower pH value
• neutral = 7
• alkaline = higher pH value

Question 4

what is the effect of acid and alkalis on the indicator litmus

Answer 4

• red in acidic
• purple in nuetral
• blue in alkaline

Question 5

what is the effect of acid and alkalis on the indicator methyl orange

Answer 5

• red in acidic
• yellow in neutral
• yellow in alkaline

Question 6

what is the effect of acid and alkalis on the indicator phenolphthalein

Answer 6

• colourless in acidic
• colourless in neutral
• pink in alkaline

Question 7

the higher the concentration of hydrogen ions in an acidic solution causes a high or low pH?

Answer 7

low pH

Question 8

the higher the concentration of hydroxide ions in an alkaline solution causes the pH to be higher or low

Answer 8

higher

Question 9

what happens to the pH of the solution when hydrogen ion concentration in the solution increases by a factor of 10

Answer 9

the pH of the solution decreases by 1

Question 10

Core Practical: Investigate the change in pH on adding
powdered calcium hydroxide or calcium oxide to a fixed volume
of dilute hydrochloric acid - METHOD

Answer 10

method
- add dilute HCl to beaker and measure pH
- add weighed mass of calcium hydroxide and stir, recording the pH
- keep adding weighed masses of calcium hydroxide until there is no more change to the pH

Question 11

Core Practical: Investigate the change in pH on adding
powdered calcium hydroxide or calcium oxide to a fixed volume
of dilute hydrochloric acid - ANALYSIS

Answer 11

analysis
- draw a line graph
-> mass on horizontal axis
-> pH on vertical axis
- line of best fit

Question 12

Explain the terms dilute and concentrated, with respect
to amount of substances in solution

Answer 12

• concentrated = larger amount of substance in given volume of solution
• dilute = lesser amount of substance in a given volume of a solution

Question 13

Explain the terms weak and strong acids, with respect to
the degree of dissociation into ions

Answer 13

• strong acid = fully dissociated in aqueous solution
• weak acid = partially dissociates in aqueous solution

Question 14

dissociation means

Answer 14

where an acid breaks down to release H+ ions in solution

Question 15

how does the strength of and acid affect its dissociation

Answer 15

• stronger acid means greater dissociation
• more H+ ions released
• the lower pH (for a given concentration of aqueous solutions

Question 16

what is a base

Answer 16

a substance that reacts with an acid to form a slat and water only

Question 17

is an acid or an alkali a soluble base

Answer 17

alkali

Question 18

the general reactions of aqueous solutions of acids with: METALS (to produce salts)

Answer 18

acid + metal -> salt + hydrogen gas

Question 19

the general reactions of aqueous solutions of acids with: METAL HYDROXIDES (to produce salts)

Answer 19

acid + metal hydroxide -> salt + water

Question 20

the general reactions of aqueous solutions of acids with: METAL OXIDES (to produce salts)

Answer 20

acid + metal oxide -> salt + water

Question 21

the general reactions of aqueous solutions of acids with: METAL CARBONATES (to produce salts)

Answer 21

acid + metal carbonate -> salt + water + carbon dioxide

Question 22

explain the general reactions of aqueous solution of acids with metal… to produce salts. - what do metal oxides and hydroxides act as

Answer 22

• metal oxides are bases (because insoluble)
• metal hydroxides are bases/alkalis if insoluble/soluble

Question 23

explian the general reactions of aqueous solution with acids with metals… how to name salts

Answer 23

• first part is name of metal in oxide/hydroxide/carbonate
• second part comes from the acid
  -> hydrochloric acid = chloride
  -> nitric acid = nitrate
  -> sulfuric acid = sulfur

Question 24

acid + base =
(Explain​ ​ the​ ​ general​ ​ reactions​ ​ of​ ​ aqueous​ ​ solutions​ ​ of​ ​ acids​ ​ with:
metals,​ ​ metal​ ​ oxides,​ ​ metal​ ​ hydroxides,​ ​ and​ ​ metal​ ​ carbonates​ ​ (all)​ ​ to
produce​ ​ salts)

Answer 24

salt + water

Question 25

how to test for hydrogen

Answer 25

- LIT splint - goes out with squeaky pop

Question 26

how to test for carbon dioxide

Answer 26

- limewater - turns cloudy

Question 27

describe a neutralisation reaction

Answer 27

a reaction between an acid and a base

Question 28

​Explain​ ​ an​ ​ acid-alkali​ ​ neutralisation​ ​ as​ ​ a​ ​ reaction​ ​ in​ ​ which​ ​ hydrogen ions​ ​ (H​ +​)​ ​ from​ ​ the​ ​ acid​ ​ react​ ​ with​ ​ hydroxide​ ​ ions (OH​-​)​ ​ from​ ​ the​ ​ alkali​ ​ to​ ​ form​ ​ water

Answer 28

- all neutralisation reactions with an acid and an alkali has an ionic equation of H+ (aq) + OH- (aq) -> H2O (l)

Question 29

what is an acid-alkali neutralisation

Answer 29

- a reaction where hydrogen ions (H+) from the acid - react with hydroxide ions (OH-) from the alkali - to form water

Question 30

explain why if soluble salts are prepared from an acid and an insoluble reactant an excess of the reactant is added

Answer 30

- to ensure your volume of acid reacts completely

Question 31

explain why if soluble salts are prepared from an acid and an insoluble reactant the excess of reactant is removed

Answer 31

- done by filtration of the insoluble reactant - is done so that you are left with just salt and water

Question 32

explain why if soluble salts are prepared from an acid and an insoluble reactant the solution remaining is only salt and water

Answer 32

- because all your acid hass fully reacted anf you have filtered off your other reactant -> the only products of your reaction are a salt and water

Question 33

explain why if soluble salts are prepared from an acid and an insoluble reactant the solution remaining is only salt and water IF YOU USE CARBONATE

Answer 33

- still only have a salt and water remaining - as carbon dioxide gas would have been given off into atmosphere

Question 34

explain why if soluble salts are prepared from an acid an a soluble reactant titration must be used

Answer 34

- both reactant are liquids/soluble so if you have an excess of one you wouldn't be able to easily remove it from you mixture of products -> so you need to measure the exact amount of volumes that react with is done easily using titration - can then mix exact proportions of the two reactants

Question 35

what is titration

Answer 35

a technique where a solution of known concentration is used to determine the concentration of an unknown solution

Question 36

​ ​ Explain​ ​ why,​ ​ if​ ​ soluble​ ​ salts​ ​ are​ ​ prepared​ ​ from​ ​ an​ ​ acid​ ​ and​ ​ a​ ​ soluble reactant the acid and the soluble reactant are then mixed in the correct proportions

Answer 36

- they are dissolved in water so cannot be filtered to remove excess - you want neutralisation with no excess reactant - to ensure a pure soluble salt is made - to find the exact amounts you can use a titration

Question 37

​ ​ Explain​ ​ why,​ ​ if​ ​ soluble​ ​ salts​ ​ are​ ​ prepared​ ​ from​ ​ an​ ​ acid​ ​ and​ ​ a​ ​ soluble reactant where the solution remaining after the reaction is only salt and water

Answer 37

- it is only salt and water because the exact amount of acid has been added to the soluble reactant -> so there is no acid or alkali as they have been completely neutralised

Question 38

Core Practical: Investigate the preparation of pure, dry hydrated copper sulfate crystals starting from copper oxide including the use of a water bath

Answer 38

method - ADD AN EXCESS OF COPPER OXIDE (insoluble) to your acid (sulfuric acid as you are making copper SULFATE) - use a FILTER and filter paper to filter off any copper oxide that hasn't reacted (your solution should be blue as copper sulfate solution has been formed) - EVAPORATE OFF THE WATER by placing your final solution in a water bath

Question 39

describe how to carry out an acid-alkali titration using burette, pipette and a suitable indicator to prepare a pure, dry salt

Answer 39

1. wash burette using acid then water 2. fill burette to 100cm cubed with acid with the meniscus' base on the 100cmcubed line 3. use 25 cm cubed pipette to add 25cm cubed of alkali into a conical flask 4. add few drops of a suitable indicator to the conical flask 5. add acid from burette to alkali until end-point is reached 6. the titre is the difference between the first and second readings on the burette 7. repeat 8. prepare pure, dry salt (warm salt solution to evaporate the water) 9. crystals form

Question 40

what is a titre

Answer 40

the volume of alkali needed to exactly neutralise the acid

Question 41

Recall the general rules which describe the solubility of common types of substances in water (soluble/insoluble) - common slats of sodium, potassium and ammonium

Answer 41

soluble

Question 42

Recall the general rules which describe the solubility of common types of substances in water (soluble/insoluble) - all nitrates

Answer 42

soluble

Question 43

Recall the general rules which describe the solubility of common types of substances in water (soluble/insoluble) - common chlorides

Answer 43

- common chlorides are soluble - except those of silver and lead

Question 44

Recall the general rules which describe the solubility of common types of substances in water (soluble/insoluble) - common sulfates

Answer 44

- common sulfates are soluble - except those of lead barium and calcium

Question 45

Recall the general rules which describe the solubility of common types of substances in water (soluble/insoluble) - common carbonates and hydroxides

Answer 45

- common carbonates and hydroxides are insoluble - except those of sodium, potassium and ammonium

Question 46

​Predict,​ ​ using​ ​ solubility​ ​ rules,​ ​ whether​ ​ or​ ​ not​ ​ a​ ​ precipitate​ ​ will​ ​ be formed​ ​ when​ ​ named​ ​ solutions​ ​ are​ ​ mixed​ ​ together,​ ​ naming​ ​ the​ ​ precipitate​ ​ if any

Answer 46

1. work out products of reaction 2. then use the general rules of solubility to determine if any salts formed are soluble or insoluble 3. INSOLUBLE salts will be formed as a precipitate (as any soluble salts will remain in solution)

Question 47

- soluble meaning - insoluble meaning

Answer 47

- soluble: can be dissolved in water - insoluble: cannot be dissolved in water

Question 48

- precipitate meaning

Answer 48

cause of a solid substance to be deposited in solid form from a solution

Question 49

describe a method used to prepare a pure, dry sample of an insoluble salt

Answer 49

1. mix two solutions needed to form the salt 2. filter mixture using filter paper (which the insoluble salt will be left on) 3. wash salt using distilled water 4. leave salt to dry on filter paper (water will evaporate, speed this process up by drying it in an oven)

Question 50

When metal Y reacts with dilute sulfuric acid, bubbles form quickly at first and then the reaction stops. Most of the solid metal remains. Explain why the reaction between metal Y and excess dilute sulfuric acid stopped even though there was solid metal Y left

Answer 50

- metal sulfate is insoluble/ forms a barrier - prevents further reaction of metal with acid