Chemical Changes

Question 1

what are alkalis?

Answer 1

soluble bases

Question 2

which pH is most acidic?

Answer 2

0 or 1

Question 3

which pH is most alkali?

Answer 3

13 or 14

Question 4

which pH is neutral?

Answer 4

7

Question 5

which ions do acids produce?

Answer 5

H+ ions in water

Question 6

which ions do alkalis produce?

Answer 6

OH- ions in water

Question 7

what are 2 ways to measure pH?

Answer 7

1: universal indicator - a wide range indicator that changes colour depending on the pH. It gives an approximate pH value
2: pH probe - gives an accurate value of the pH

Question 8

what is the neutralisation reaction?

Answer 8

acid + base > salt + water

H+ + OH- > H2O

Question 9

what are titrations?

Answer 9

used to find the exact volume of acid needed to neutralise a quantity of alkali (or vice versa). the results can be used to calculate the acid or alkali concentration.

Question 10

what is the metal carbonate reaction?

Answer 10

acid + metal carbonate > salt + water + carbon dioxide

Question 11

what is the metal oxide reaction?

Answer 11

acid + metal oxide > salt + water

Question 12

what is the metal hydroxide reaction?

Answer 12

acide + metal hydroxide > salt + water

Question 13

how are soluble salts made?

Answer 13

by adding metals or insoluble metal compounds to acids. The excess solid is filtered off and the remaining salt solution is crystallised.

Question 14

what is a strong acid?

Answer 14

an acid that completely ionises (dissociates) in water to produce hydrogen ions
- hydrochloric acid
- sulfuric acid
- nitric acid

Question 15

what is a weak acid?

Answer 15

an aci that partially ionises (dissociates) in water to produce hydrogen ions
- ethanoic acid
- citric acid
- carbonic acid

Question 16

what is pH?

Answer 16

a measure of the concentration of H+ ions in a solution

Question 17

what happens when the pH of a solution changes by X?

Answer 17

the H+ ion concentration chages by a factor of 10^-x

Question 18

what is acid strength?

Answer 18

a measure of the proportion of acid molecules that ionise in water

Question 19

what is acid concentration?

Answer 19

a measure of the number of acid molecules in a certain volume of water

Question 20

which metals of the reactivity series can be exracted from molten compounds using electrolysis (top 5)?

Answer 20

Potassium
Sodium
Lithium
Calcium
Magnesium

Question 21

what comes after the electrolysis 5?

Answer 21

carbon

Question 22

which 3 can be extracted from their oxides by reduction using carbon?

Answer 22

Zinc
Iron
(Hydrogen)
Copper

Question 23

what is the metal + oxygen reaction?

Answer 23

metal + oxygen > metal oxide

Question 24

what is the metal + acid reaction?

Answer 24

metal + acid > salt + hydrogen

Question 25

what is the metal + water reaction?

Answer 25

metal + water > metal hydroxide + hydrogen

Question 26

which elements have an explosive reaction to cold, dilute acid AND a reaction to water?

Answer 26

Potassium Sodium Lithium Calcium

Question 27

which elements have a moderate reaction to cold, dilute acid BUT no reaction to water?

Answer 27

Magnesium Zinc Iron

Question 28

which element has no reaction to either cold, dilute acid OR water?

Answer 28

copper

Question 29

what is a displacement reaction?

Answer 29

when a more reactive element displaces a less reactive metal from its compound

Question 30

what is oxidation?

Answer 30

gain of oxygen loss of electrons

Question 31

what is reduction?

Answer 31

gain of electrons loss of oxygen

Question 32

what is a redox reaction?

Answer 32

where one substance in a reaction is reduced and another is oxidised

Question 33

Fe + CuSO4 > FeSO4 + Cu; which is the oxidation and which is the reduction?

Answer 33

Fe loses 2 electrons to become Fe2+ + 2e- so it’s oxidised Cu2+ gains 2 electrons to become Cu so it’s reduced

Question 34

what are ionic equations?

Answer 34

they only show the particles that react and the products they form

Question 35

what is the ionic equation of magnesium + aqueous zinc chloride > aqueous magnesium chloride + zinc?

Answer 35

Mg + Zn2+ > Mg2+ + Zn

Question 36

what would we call the chloride ions?

Answer 36

spectator ions

Question 37

what is an electrolyte?

Answer 37

a liquid or solution that can conduct electricity because ions are free to move

Question 38

what happens to the positive metal ions (Pb2+)?

Answer 38

they move towards the cathode and are reduced Pb2+ + 2e- > Pb

Question 39

what happens to the negative non-metal ions (Br-)?

Answer 39

they move towards the anode and are oxidised 2Br- > Br2 + 2e-

Question 40

what happenes in the electrolysis of aqueous CuSO4?

Answer 40

metal produced at the cahtode if it is less reactive than H2 O2 and H2O are produced at anode if no halide ions are present

Question 41

what happens in the electrolysis of aqueous NaCl?

Answer 41

H2 produced at the cathode if metal is more reactive than H2 Halogen produced at the anode if halide ions are present