Electrochemistry

Question 1

Electrolysis definition

Answer 1

Electrical energy used to cause a non-spontaneous chemical reaction to occur

Question 2

Which side of battery electrons come out from

Answer 2

Short side

Question 3

Which side of the battery are the anode and cathode connected to

Answer 3

Anode connected to the positive side (long side) –> positively charged
Cathode connected to the negative side (short side) –> negatively charged

Question 4

Cathode and anode attract what

Answer 4

Cathode attract cation anode attract anion

Question 5

What happens to binary ionic compounds after electrolysis

Answer 5

Decompose to form a metal and a non metal

Question 6

Molten compounds what happens to the metal

Answer 6

Silvery liquid collected at bottom of the reaction vessel (near the cathode)

Question 7

What state is bromine at room temp

Answer 7

liquid

Question 8

OH- oxidation equation

Answer 8

4OH- –> O2 + 2H2O + 4e-

Question 9

Cathode selective discharge electrochem series

Answer 9

Less reactive metals accept ions more readily and will be discharged at the cathode
More reactive have greater tendency to form ions and will remain in the electrolyte

Question 10

Electrochem series

Answer 10

Same as reactivity series

Question 11

Conc of anion (halides)

Answer 11

Greater conc will be preferentially discharged over OH-

Question 12

What are the inert and non inert electrodes

Answer 12

Inert: Platinum, graphite
Non intert: Copper, Silver

Question 13

Electrolysis of water equation

Answer 13

Anode:
4OH - —> O2 + 2H2O + 4e-
2H2O —> O2 + 4e- + 4H+

Cathode:
2H+ + 2e- –> H2
2H2O + 2e- –> H2 + 2OH-

Overall: 2H2O –> O2 + 2H2

Question 14

Electroplating anode cathode electrolyte

Answer 14

anode: plating metal
cathode: substance to be plated
electrolyte: must contain the ions of the plating metal

Question 15

What happens in the purification of copper

Answer 15

As one copper atom is oxidised at the anode to form copper (II) ion and enters the solution, a copper (II) ion is reduced at the cathode to form copper and is deposited on the cathode

Question 16

What is a simple cell

Answer 16

A spontaneous redox reaction that produces electrical energy

Question 17

Simple cell what is cathode/anode

Answer 17

More reactive is anode
Less reactive is cathode

Question 18

Explain simple cells

Answer 18

More reactive metal undergoes oxidation at the anode and electrons flow through the wire to the cathode (produces current and cause deflection in galvanometer)

Cathode provides surface for electron transfer and ions at bottom of Electrochem series will be dis charged

Question 19

What kind of acid does chlorine dissolve to form

Answer 19

Oxidising acid that will bleach universal indicator

The anode go from green to red to colourless (bleached)

Question 20

Colour change (indicator) at cathode when hydrogen is discharged

Answer 20

Go from green (original) to red (when H+ ions are there) to greenish-blue (when they hydrogen gas is no longer there)

Question 21

Aqueous copper (II) sulfate electrolysis overall equation

Answer 21

2CuSO4 + 2H2O –> O2 + 2H2 + 2H2SO4

Question 22

Phrasing for copper being deposited

Answer 22

Reddish-brown solid deposited at the cathode

Question 23

Hydrogen gas

Answer 23

1. Flammable gas
2. An electrical insulator and can stop the production of an electrical current when formed at the cathode

Question 24

Fuel cell equations

Answer 24

Anode (hydrogen)
H2 + 2OH- –> 2H2O + 2e-

Cathode (oxygen)
O2 + 2H2O + 4e- –> 4OH-