Chemical Changes

Question 1

metal + oxygen = ?

Answer 1

metal oxide

Question 2

metal + water = ?

Answer 2

metal hydroxide + hydrogen

Question 3

metal + acid = ?

Answer 3

salt + hydrogen

Question 4

metal oxide + acid = ?

Answer 4

salt + water

Question 5

metal hydroxide + acid = ?

Answer 5

salt + water

Question 6

what is oxidation?

Answer 6

the loss of electrons

Question 7

what is reduction?

Answer 7

the gain of electrons

Question 8

list the reactivity series.

Answer 8

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

Question 9

metal carbonate + acid = ?

Answer 9

salt + water + carbon dioxide

Question 10

what happens in a displacement reaction?

Answer 10

a more reactive metal will displace a less reactive metal from a compound

Question 11

which metals react with cold water?

Answer 11

• K, Na, Li, and Ca fizz in cold water
• Mg will fizz slightly over a longer period of time

Question 12

which metals react with dilute acids?

Answer 12

most more reactive than hydrogen (potassium, sodium, lithium, calcium, magnesium, zinc, iron)

Question 13

what do metals form when they react?

Answer 13

positive ions

Question 14

what is a spectator ion?

Answer 14

an ion that doesn’t change within a reaction

Question 15

what is the reduction half equation?

Answer 15

x^+ + e^- = x

Question 16

what are the 2 oxidation half equations?

Answer 16

• x^- = x + e^-
• x = x^+ + e^-

Question 17

what are the diatomic elements?

Answer 17

hydrogen, nitrogen, fluorine, oxygen, iodine, chlorine, bromine (have no fear of ice cold beverages)

Question 18

what is an ore?

Answer 18

a rock containing a metal compound which metal can be extracted from for a profit

Question 19

what are 3 types of metal extraction?

Answer 19

• electrolysis
• displacement using carbon (any less reactive than carbon)
• thermal decomposition (mercury, silver)

Question 20

why does gold not need to be extracted from ores?

Answer 20

it is unreactive so is found pure in the earth

Question 21

what is the formula for hydrochloric acid?

Answer 21

HCl

Question 22

what salt does hydrochloric acid form?

Answer 22

chloride

Question 23

what is the formula for nitric acid?

Answer 23

HNO3

Question 24

what salt does nitric acid form?

Answer 24

nitrate

Question 25

what is the formula for sulphuric acid?

Answer 25

H2SO4

Question 26

what salt does sulphuric acid form?

Answer 26

sulphate

Question 27

what is an acid?

Answer 27

a substance which contains H+ ions which are released when it is dissolved in water

Question 28

what does a low pH mean?

Answer 28

high concentration of H+ ions

Question 29

what is a strong acid?

Answer 29

where all molecules ionise - dissociate into ions

Question 30

what is a weak acid?

Answer 30

where only small fraction of molecules ionise - dissociate into ions - reversible and never goes to completion

Question 31

what is a concentrated acid?

Answer 31

lots of acid dissolved - high number of moles per dm^3

Question 32

what is a dilute acid?

Answer 32

small amount of acid dissolved - low number of moles per dm^3

Question 33

give the ionic equation for a neutralisation reaction

Answer 33

H^+ + OH^- → H2O

Question 34

what is pH?

Answer 34

a measure of the H+ concentration in solution

Question 35

what happens as pH decreases by 1 unit?

Answer 35

concentration of H+ ions increase by a factor of 10

Question 36

what is an alkali?

Answer 36

a substance which releases OH- ions when added to water

Question 37

what is a base?

Answer 37

a compound which neutralises acids

Question 38

give 3 examples of bases

Answer 38

metal oxides, metal hydroxides, metal carbonates

Question 39

what is electrolysis?

Answer 39

splitting of a compound using flow of charge

Question 40

what is an electrolyte?

Answer 40

ionic compound that is molten or dissolved in water that conducts electricity and is decomposed by it

Question 41

what is an electrode?

Answer 41

unreactive material which can conduct electricity - usually graphite

Question 42

why is graphite used for electrodes?

Answer 42

- it has a high MP - it is inert - it conducts electricity

Question 43

what is the charge of anode and cathode in electrolysis?

Answer 43

positive anode, negative is cathode

Question 46

what is the product at the anode in electrolysis?

Answer 46

halogen gas (if anion is group 7) or oxygen (if anion is not group 7)

Question 47

what is cryolite?

Answer 47

aluminium compound with a lower melting point than aluminium oxide

Question 48

why is cryolite used in electrolysis?

Answer 48

using molten cryolite as a solvent reduces some of the energy costs involved in extracting aluminium by allowing the ions in aluminium oxide to move freely at a lower temperature.

Question 49

what is the process at the anode in electrolysis?

Answer 49

oxidation

Question 50

give the half equation at the anode in electrolysis

Answer 50

X^- = e^- + X

Question 51

what is the product at the cathode in electrolysis?

Answer 51

metal (if cation is less reactive than hydrogen) or hydrogen (if cation is more reactive than hydrogen)

Question 52

what is the process at the cathode in electrolysis?

Answer 52

reduction

Question 53

give the half equation at the cathode in electrolysis

Answer 53

X^+ + e^- = X

Question 54

what is an anion?

Answer 54

negative ion

Question 55

what is a cation?

Answer 55

positive ion

Question 56

what is uncertainty?

Answer 56

systematic error which affects everything the same

Question 57

what colour is phenolphthalein?

Answer 57

- pink in alkali - colourless in acid

Question 58

what is titration used for?

Answer 58

to make a soluble salt from an acid and soluble base it is the best method to make sure reactants are mixed in correct proportions

Question 59

what are the control variables in titrations?

Answer 59

concentration and volume of acid

Question 60

what are concordant results?

Answer 60

within 0.1 of each other

Question 61

a piece of magnesium is placed in a solution of copper(II) sulfate; describe what you would observe.

Answer 61

magnesium would displace copper so a brown solid appears over the magnesium and the blue solution becomes paler

Question 62

compare the electrolysis of molten magnesium chloride with the electrolysis of aqueous magnesium chloride.

Answer 62

in MOLTEN: - high temperature required to melt MgCl2 - Mg2+ ions attracted to cathode - Mg2+(l) + 2e- ⇒Mg(s) - Cl- ions attracted to anode - 2Cl- ⇒Cl2(g) +2e- in AQUEOUS: - carried out at RT - mixture of ions present: Mg2+, H+, Cl-, OH- - Mg2+ and H+ ions attracted to cathode; hydrogen is less reactive than Mg and is more easily reduced so 2H+(l) + 2e- ⇒ H2(g) - Cl- and OH- ions attracted to anode; chlorine is a halogen so 2Cl-(l) ⇒ Cl2(g) + 2e-