required practical - electrolysis

Question 1

what is electrolysis

Answer 1

separating ionic compounds into their pure elements

Question 2

what is an electrolyte

Answer 2

liquid or solution containing an ionic compound

Question 3

what state must the ions be in order for electrolysis to occur

Answer 3

liquid - ions are free to move around

Question 4

how does electrolysis work

Answer 4

by using the battery to pass an electric current through the electrolyte

Question 5

explain the process of basic and molten compounds of electrolysis

Answer 5

1. the negative compound ( for example bromine) ions are attracted to the positive anode, atoms are discharged and form a gas which floats away
2. electrons from the bromine are transported from the anode to the cathode to be given to the metal (lead) ions which are attracted to the cathode - turning it into pure metal (lead)

Question 6

explain how metal electrolysis works and why there are extra steps that need to be completed

Answer 6

when a metal is being used their ions are not free to move and therefore must be turned to molten first
the steps are
- purify the metal
- mix with cryolite to lower the melting point
- then melt

then follow the steps for normal electrolysis

Question 7

what is an aqueous solution

Answer 7

compounds that have been dissolved in water

Question 8

explain how aqueous solutions undergo electrolysis

Answer 8

1. set up is the same as for normal electrolysis
2. the main difference is figuring out which ions go to which electrode. this is because as well as the ions from each compound there will also be hydrogen ions and hydroxide ions from the water
   - H2O ——> H+ + OH-

Question 9

What is the first rule of aqueous solution electrolysis

Answer 9

• the negative cathode will only attract positive ions - the metal and the hydrogen ions
• because the cathode can only discharge one and therefore the ions which is less reactive will be discharged ( if it is more reactive then hydrogen)

Question 10

what is the second rule of aqueous solution electrolysis

Answer 10

• the positive anode will only attract negative ions - the metal and the hydroxide
• because the anode can only discharge one and therefore if a halide is present ( group 7) then it automatically gets discharged
• if not then it is always the hydroxide ion