Chemical changes

Question 1

What is neutralisation?

Answer 1

when an alkali neutralises an acid to form salt and water

Question 2

what is the neutralisation symbol equation

Answer 2

H+ + OH- becomes H2O
. H+(aq)
. OH- (AQ)

Question 3

what ions do acids produce in aqueous solutions

Answer 3

H+ ions

Question 4

What ions do alkaline produce in aqueous solutions

Answer 4

OH- ions

Question 5

what is used to measure ph

Answer 5

ph probe or universal indicator

Question 6

what ph do acids have

Answer 6

less than 7

Question 7

what ph do alkali have

Answer 7

greater than 7

Question 8

what is the ph of a neutral solution

Answer 8

7

Question 9

what is the formula to find ph

Answer 9

10 to the power (-x)

Question 10

what are titration experiments used for

Answer 10

to find the the concentration of unknown substances

Question 11

describe the titration experiment

Answer 11

1.Fill up a burette with acid using a funnel.
2.Use a volumetric pipette to add 25cm3 of alkali to a conical flask.
3. Add an indicator to the alkali.
4.The acid from the burette is allowed to run into the alkali slowly , swirling constantly to ensure the reactants mix well.
5. Slow the adding of acid when the indicator changes colour, add in the acid drop by drop.
6. Stop adding acid when there is a permanent colour change.
7. Record the volume of acid delivered.
8. The titration is repeated until concordant (within 0.1 cm³) titres are obtained.

Question 12

what are strong acids

Answer 12

completely ionised in an aqueous solution and have high concentration of H+ ions.

Question 13

what are weak acids

Answer 13

partially ionise in an aqueous solution and have a low concentration of H+ ions.

Question 14

give some examples of strong acids

Answer 14

hydrochloric acid
nitric acid
sulfuric acid

Question 15

give some examples of weak acids

Answer 15

ethanoic acid
citric acid
carbonic acid

Question 16

What is oxidation

Answer 16

Loss of electrons or the gain of oxygen

Question 17

What is reduction

Answer 17

Gain of electrons and loss of oxygen

Question 18

Metals react with oxygen to produce?

Answer 18

Metal oxides

Question 19

What is displacement

Answer 19

When a more reactive displaces a less reactive metal from its compound

Question 20

Give some examples of unreactive metals

Answer 20

Gold
Platinum

Question 21

Acids + metals is ?

Answer 21

Salt + hydrogen

Question 22

Acid + metal hydroxide is

Answer 22

Salt + water

Question 23

Acid + metal oxide

Answer 23

Salt + water

Question 24

Acid + metal carbonate is

Answer 24

Salt + water + CO2

Question 25

Metal + water

Answer 25

Metal hydroxide and hydrogen

Question 26

what is electrolysis

Answer 26

passing electric current through molten or solutions of aqueous ionic compounds so that they decompose or break down

Question 27

what is an electrolyte

Answer 27

solutions of molten or aqueous ionic compounds that are able to conduct electricity

Question 28

why must ionic compounds be molten or aqueous in electrolysis

Answer 28

so ions are free to move and carry a charge to conduct electricity

Question 29

what is an electrode

Answer 29

a rod of metal or graphite through which an electric current flows into or out of an electrolyte

Question 30

what is an anode

Answer 30

positive electrode

Question 31

what is a cathode

Answer 31

negative electrode

Question 32

what are cations

Answer 32

positive ions

Question 33

what are anions

Answer 33

negative ions

Question 34

which electrode is the positive ions attracted to

Answer 34

cathode

Question 35

which electrode is the negative ions attracted to

Answer 35

anode

Question 36

which part of REDOX happens at the anode

Answer 36

oxidation

Question 37

which part of REDOX happens at the cathode

Answer 37

reduction

Question 38

in the electrolysis of an aqueous solution of ionic compounds. what are the potential ions that are discharged

Answer 38

hydrogen ions or the metal ions

Question 39

in the electrolysis of an aqueous solution of ionic compounds. what determines which ions are discharged at the cathode

Answer 39

if the metal is more reactive than hydrogen, then hydrogen is produced. if the metal is less reactive than hydrogen, then the metal ion is discharged

Question 40

in the electrolysis of aqueous solutions of ionic compounds, what are the potential ions that could be discharged at the anode

Answer 40

it could be the halide ions that are discharged or hydroxide ions that are discharged.

Question 41

in the electrolysis of an aqueous solution of ionic compounds. what determines which ions are discharged at the anode

Answer 41

if it's a halide, then halide ions are discharged if it's not a halide, then hydroxide ions are discharged

Question 42

what is the half equation for when hydroxide ions are discharged at the anode in aqueous solutions of ionic compounds

Answer 42

4OH- to O2 + 2H20 + 4e-

Question 43

write the half equation for molten lead bromide in electrolysis

Answer 43

Pb2+ + 2e– ⟶ Pb 2Br- ⟶ Br2 + 2e– . Lead ions are reduced . Bromide ions are oxidised

Question 44

Dilute hydrochloric acid is a strong acid. Explain how the acid is strong and dilute at the same time

Answer 44

It's strong because the acid fully ionises in aqueous solution and it's dilute because there's a small amount of acid per unit volume of solution

Question 45

Why is a Burette preferred/ what is it's role

Answer 45

measurement of variable volume

Question 46

why is excess used zinc used instead of hydrochloric acid

Answer 46

excess zinc can be filtered off

Question 47

describe how the other student could obtain pure crystals of zinc chloride from zinc chloride solution

Answer 47

heat (the solution) until crystallisation point is reached leave solution to crystalise

Question 48

explain how the alkaline solution (NaOH) is produced in the electrolysis of aqueous soltion of sodium chloride

Answer 48

sodium ions and hydroxide ions are left in the solution the hydrogen ions are discharged at the cathode the chloride ions are discharged at the anode

Question 49

Aluminium also reduces silicon dioxide. Carbon is used rather than aluminium to reduce silicon dioxide because carbon is cheaper than aluminium. Carbon can be obtained by heating coal. Aluminium is obtained from aluminium oxide. Explain why aluminium is more expensive than carbon.

Answer 49

more energy is needed to obtain aluminium because aluminium is obtained by electrolysis