chemical changes

Question 1

how can you measure pH

Answer 1

• indicator (chemical dyes which change colour)

- pH probe and pH meter

Question 2

what does a neutralisation reaction produce

Answer 2

a salt and water

Question 3

what is a strong acid

Answer 3

an acid which ionises completely in an aqueous solution to release H^+ ions

Question 4

what is a weak acid

Answer 4

an acid that only partially dissociates in an aqueous solution to release H^+ ions, the reaction is reversible and the equilibrium lies to the left

Question 4

what is a weak acid

Answer 4

an acid that only partially dissociates in an aqueous solution to release H^+ ions, the reaction is reversible and the equilibrium lies to the left

Question 5

what is concentration

Answer 5

how much acid there is in a certain volume

Question 6

what does a decrease of one on the pH scale represent in terms of hydrogen ions

Answer 6

10x more hydrogen ions

Question 7

what is the strength of an acid

Answer 7

the proportion of acid molecules which dissociate into hydrogen ions

Question 7

what is the strength of an acid

Answer 7

the proportion of acid molecules which dissociate into hydrogen ions

Question 8

what are the products when you react a metal oxide or hydroxide with acid

Answer 8

salt + water

Question 9

what are the products when you react a metal and an acid

Answer 9

salt + hydrogen

Question 10

what are the products when you react a metal with water

Answer 10

metal hydroxide + hydrogen

Question 11

what is oxidation

Answer 11

the process of gaining oxygen

Question 12

what is reduction

Answer 12

the loss of oxygen

Question 13

what happens when you react a metal oxide with carbon

Answer 13

the oxygen from the metal oxide will leave to form carbon dioxide, leaving a pure metal

Question 14

what metals can you react with carbon for extraction

Answer 14

• zinc
• iron
• copper

Question 14

what metals can you react with carbon for extraction

Answer 14

• zinc
• iron
• copper

Question 15

what does OILRIG stand for

Answer 15

oxidation is loss (of electrons)

reduction is gain (of electrons)

Question 16

what is an electrolyte

Answer 16

a liquid or solution that contains an ionic compound (the ions must be free to move)

Question 17

what is an electrode

Answer 17

solid conductors made of metal or carbon

Question 18

what is the name of the positive electrode

Answer 18

the anode

Question 19

what is the name of the negative electrode

Answer 19

the cathode

Question 20

how does separation happen during electrolysis

Answer 20

• the positive ions are attracted to the cathode
• at the cathode they gain electrons and become a neutral atom
• the negative ions are attracted to the anode
• at the anode they become discharged and become a neutral atom

Question 21

at which electrode does oxidation take place

Answer 21

the anode

Question 22

at which electrode does reduction take place

Answer 22

the cathode

Question 23

in which ore is aluminium oxide found in

Answer 23

bauxite

Question 24

why do we mix aluminium oxide with cryolite when trying to melt it

Answer 24

it lowers the melting point

Question 25

in the electrolysis of aqueous solutions, what other ions will there be

Answer 25

H^+ and OH^-

Question 26

during the electrolysis of an aqueous solution, which ions will the cathode attract

Answer 26

H^+ and the positive ion in the dissolved compound

Question 27

during the electrolysis of an aqueous solution, what will the anode attract

Answer 27

OH^- ions and the negative ions of the dissolved compound

Question 28

which ion will the discharged at the cathode

Answer 28

the least reactive one

• in most cases hydrogen
• but copper is less reactive than hydrogen

Question 29

which ion will the discharged at the anode

Answer 29

• if a halide is present, then the halide

- if a halide isn’t present, the hydroxide ion