unit 4 chemical changes (electrolysis - checklist given in class)

Question 1

explain what happens at the cathode

Answer 1

positive ions are attracted and gain electrons in reduction

Question 2

at which electrode would zn2+ (aq) turn into zn (s)

Answer 2

negative electrode

Question 3

Why must ionic compounds be liquid or dissolved in water for electrolysis to work

Answer 3

so ions can move and carry charge

Question 4

explain what happens at the anode

Answer 4

negative electrons are attracted and lose electrons in oxidation

Question 5

what is electrolysis

Answer 5

using electricity to break down an ionic compound into elements

Question 6

at which electrode would cl-(aq) turn into cl2(g)?

Answer 6

positive electrode

Question 7

complete the half equation
Al3+ + __ = ___

Answer 7

Al3+ + 3e- = Al

Question 8

complete the half equation
cl- = ___ + ___

Answer 8

2cl- = cl2 + 2e-

Question 9

complete the half equation
__o2- = ____ + ____

Answer 9

2o2- = o2 + 4e-

Question 10

what will be the products for the electrolysis of molten iron bromide

Answer 10

iron and bromide

Question 11

what will be the products for the electrolysis of molten zinc oxide

Answer 11

zinc and oxygen

Question 12

what is the disadvantages of using electrolysis

Answer 12

requires a large amount of electrical energy which is expensive

Question 13

Why is aluminium oxide mixed with cryolite when extracting aluminium

Answer 13

to lower the melting point

Question 14

what is produced at the anode and cathode in the electrolysis of aluminium oxide

Answer 14

aluminium at the cathode and oxygen at the anode

Question 15

why does the anode need to be replaced in the electrolysis of aluminium oxide

Answer 15

the oxygen reacts with the carbon electrode to produce carbon dioxide

Question 16

where does oxygen come from in electrolysis of solutions

Answer 16

hydroxide ions from water

Question 17

where does hydrogen come from in electrolysis of solutions

Answer 17

water

Question 18

when is hydrogen made at the negative electrode in solutions

Answer 18

if the metal is more reactive than hydrogen

Question 19

when is oxygen made at the positive electrode in solutions

Answer 19

if the non-metal ion is not a halide

Question 20

which 2 ions are involved in electrolysis when water is present

Answer 20

H+ ions and OH- ions