ES

Question 1

define electrolysis

Answer 1

breaking down of a substance using electricity

Question 2

what are the conditions required for electrolysis

Answer 2

ionic compounds that are molten or dissolved in solution as the ions will be free to move around

Question 3

properties of an electrode

Answer 3

inert and can conduct electricity - eg graphite

Question 4

in electrolysis of an aqueous solution, what is formed at the cathode

Answer 4

.if the metal is less reactive than hydrogen, the metal will form. if the metal is
.if the metal is more reactive than hydrogen, hydrogen will form

Question 5

in electrolysis of an aqueous solution, what is formed at the anode

Answer 5

.if the solution doesn’t contain a halide ion then oxygen from OH- will form.

.if the solution is concentrated and contains a halide ion, then the halogen will form

.if it is dilute, oxygen will form

Question 6

can you obtain chlorine from the electrolysis of sodium chloride

Answer 6

only if the solution is concentrated. if it is dilute, then oxygen from the OH-ions will form at the anode.

Question 7

give the equation of oxygen being formed at the anode

Answer 7

4OH(-) –> 2H20 + O2 + 4e-

Question 8

what is a reducing agent

Answer 8

something that is being oxidised

Question 9

what is an oxidising agent

Answer 9

something that is being reduced

Question 10

colours and states of group 7 elements

Answer 10

fluorine - pale yellow gas
chlorine - green gas
bromine - brown liquid
iodine - grey solid

Question 11

trend of boiling points in group 7 and why

Answer 11

increases as you go down the group due to the increasing idid due to increasing size and relative mass of atoms.

Question 12

what is electronegativity

Answer 12

ability of an atom to attract electrons towards itself in a covalent bond

Question 13

trend in electronegativity in group 7

Answer 13

decreases down the group due to:

. larger atomic radius and size - means that there is less attraction between the positive nucleus and bonding electrons

. more shielding - makes it more difficult for atom to attract electrons

Question 14

reactivity trends in group 7

Answer 14

decreases as you go down a group, due to larger atomic size meaning less attraction from positive nucleus.

Question 15

what are hydrogen halides and how are they formed

Answer 15

a molecule that contains a hydrogen bonded to a halogen. they’re gases that dissolve in water to form an acidic solution (eg HCl)

Question 16

trend in bond enthalpies (strength of bond) as you go down group 7 and why

Answer 16

decreases because there is less attraction between the nucleus and the outermost electrons

Question 17

test for halide ions with silver nitrate

Answer 17

1. add nitric acid to solution
2. then add silver nitrate to solution

. if chloride is present, white precipitate is formed (silver chloride)
. if bromide is present, cream precipitate is formed (silver bromide)
. if iodide is present, yellow precipitate is formed (silver iodide)

Question 18

uses of chlorine water

Answer 18

.added to drinking water to sterilise it (kills harmful micro-organisms) - allows us to drink and swim in it.

.used to make bleach

Question 19

risks of chlorine

Answer 19

it is risky when transporting as it is toxic and corrosive and must be kept away from eyes.

Question 20

atom economy equation

Answer 20

(mr of desired product) / (mr of all products) x 100

Question 21

what affects equilibrium position

Answer 21

temperature and pressure affect equilibrium but concentration doesn’t