Topic 4: chemical changes

Question 1

what is oxidation

Answer 1

what a substance gains oxygen

Question 2

what is reduction

Answer 2

when a substance loses oxygen

Question 3

describe the reactivity series of metals

Answer 3

the series shows the metals in order of their reactivity

Question 4

list the reactivity series

Answer 4

potassium
sodium
lithium
calcium
magnesium
aluminium
carbon
zinc
iron
lead
hydrogen
copper
silver
gold

Question 5

what is a displacement reaction

Answer 5

a reaction where a more reactive metal displaces a less reactive metal from a compound

Question 6

how are unreactive metals found in earth

Answer 6

in their natural state

Question 7

how can metals less reactive than carbon be exerted

Answer 7

reduction with carbon. carbon displaces the metal in a metal oxide - gets oxidised to carbon oxides. metal from the metal oxides gets reduced to the pure metal

Question 8

how metals more reactive than carbon be extracted

Answer 8

by electrolysis

Question 9

how is oxidation defined in terms of electron transfer

Answer 9

loss of electrons

Question 10

how is reduction defined in terms of electron transfer

Answer 10

gain of electrons

Question 11

general equation for a reaction between metals and acids

Answer 11

metal + acid = salt + hydrogen

Question 12

which metals in the reactivity series will react with acid

Answer 12

those above hydrogen

Question 13

general equation for neutralisation reaction

Answer 13

base + acid = salt + water

Question 14

general equation for the reaction between metal carbonate and acid

Answer 14

metal carbonate + acid = salt + water + carbon dioxide

Question 15

general equation for the reaction between metal oxides and acids

Answer 15

metal oxide + acid - a salt + water

Question 16

what is a redox reaction

Answer 16

a reaction where both oxidation and reduction occurs

Question 17

how is a soluble salt formed

Answer 17

react the excess with some insoluble chemical
filter off leftovers
crystallise the product

Question 18

what acids and alkalis produce in aqueous solutions

Answer 18

acids produce hydrogen ions
alkalis produce hydroxide ions

Question 19

what are bases

Answer 19

bases are compounds that neutralise acids

Question 20

what do acids produce in aqueous solutions

Answer 20

acids produce hydrogen ions in aqueous solutions

Question 21

what do alkalis produce in aqueous solutions

Answer 21

alkalis are soluble bases, producing hydroxide ions in aqueous solutions

Question 22

what is a PH scale

Answer 22

the measure of acidity or alkalinity of a solution

Question 23

what does PH 7 show

Answer 23

a neutral solution

Question 24

what are strong acids on the ph scale

Answer 24

0,1,2,3

Question 25

what are weaker acids on the ph scale

Answer 25

4,5,6

Question 26

what is weaker alkalis on the ph scale

Answer 26

8,9,10

Question 27

what are strong alkaline of the ph scale

Answer 27

11,12,13,14

Question 28

what is a strong acid definition

Answer 28

strong acid is completely ionised in aqueous solution

Question 29

what is a weak acid

Answer 29

weak acid is only partially ionised in aqueous solutions

Question 30

what happens to ph as concentration of hydrogen atoms increase

Answer 30

the ph decreases

Question 31

what is a the difference between concentrated acids and diluted acids

Answer 31

concentrated acid has more moles of acid per unit volume than dilute

Question 32

is concentrated and dilute acids the same as strong and weak acids

Answer 32

no concentration is not the same thing as strength

Question 33

what does it mean when someone refers to the strength off an acid

Answer 33

strength refers to whether the acid is completely ionised in water or only partially

Question 34

as the ph is decreased by one unit, what change is seen in the hydrogen ion concentration

Answer 34

increases by a factor of 10

Question 35

what is electrolysis

Answer 35

the passing of an electric current through ionic substances that are molten or in solution to break them down into elements; ions are discharged at electrodes to produce these

Question 36

what is an electrolyte

Answer 36

the liquid/solution which conducts electricity

Question 37

what is a cathode

Answer 37

a negative electrode

Question 38

what is an anode

Answer 38

a postive electrode

Question 39

what occurs at the cathode during electrolysis

Answer 39

reduction occurs

Question 40

what occurs at the anode during electrolysis

Answer 40

oxidation occurs

Question 41

in aqueous electrolysis, which element is discharged at the cathode

Answer 41

the less reactive element discharges at the cathode. hydrogen is produced unless there is a less reactive metals in which the metal is produced.

Question 42

oxygen is produced at the anode, unless what happens...

Answer 42

unless the solution contains halide ions in which case halogen molecules are produced

Question 43

how is aluminium manufactured?

Answer 43

aluminium is made through the electrolysis of aluminium oxide and cryolite

Question 44

why is producing aluminium so expensive

Answer 44

lots of energy is needed to produce the current in electrolysis which makes the process so expensive

Question 45

why is cryolite used in the manufacturing of aluminium

Answer 45

it lowers the the melting point of aluminium oxide, reducing energy costs

Question 46

which metals do not react with acids

Answer 46

copper silver gold

Question 47

how can you identify an acid ad metal from a salt

Answer 47

the metal is the same as the metal in the salt, and the acid name matches the non-metal part of the salt

Question 48

name the acid used to make sodium chloride

Answer 48

hydrochloric acid

Question 49

name the acid used to make iron nitrate

Answer 49

nitric acid

Question 50

name the acid used to make iron nitrate

Answer 50

nitric acid

Question 51

name the acid used to make copper sulphate

Answer 51

sulphuric acid

Question 52

name the acid used to calcium carbonate

Answer 52

carbonic acid

Question 53

what was the chemical formula of hydrochorlic acid

Answer 53

HCL

Question 54

what is the chemical formula of nitric acid

Answer 54

HNO3

Question 55

what is the chemical formula of sulphuric acid

Answer 55

H2SO4

Question 56

what is the chemical formula of carbonic acid

Answer 56

H2CO3

Question 57

what are the three key steps in preparing a salt from an acid and a metal

Answer 57

add excess metal to acid until it stops fizzing. filter off unreacted metal. evaporate off some of the water and leave to cool and crystallise

Question 58

how can prepared salt be dried

Answer 58

by patting dry with filter paper

Question 59

how should a salt solution be heated

Answer 59

gently with a water bath

Question 60

when describing the preparation of a salt, how can you be specific to the exam question

Answer 60

by naming the acid and metal needed to make the salt

Question 61

when adding metal to acid in preparation of a salt, what is used to contain the reaction

Answer 61

a beaker

Question 62

what 3 other substances can be used to prepare a soluble salt other than a metal

Answer 62

metal oxide metal hydroxide metal carbonate