7. electricity and chemical change

Question 1

conduction

Answer 1

1. only solids that conduct are metals and carbon (graphite)
   2.molecular substances are non-conductors
2. ionic compounds don’t conduct when solid but conduct when melted or dissolved in water

Question 2

electrolysis

Answer 2

decomposition of an ionic compound when molten or in aqueous solution by the passage of an electric current

Question 3

positive electrode

Answer 3

anode

Question 4

negative electrode

Answer 4

cathode

Question 5

during electrolysis

Answer 5

positive ions go to negative electrode so anion to anode
negative ions go to positive electrode so cations to cathode

Question 6

why does decomposition occur

Answer 6

1 electrons flow along wire from negative terminal of the battery to the cathode
2 in liquid the ions carry the current and move to electrode of opposite charge
3 at cathode, cations accept electrons
4 at anode, anions give up electrons
5 electrons flow along the wire from anode to the positive terminal of the battery

Question 7

rules for electrolysis of a solution: CATHODE

Answer 7

metal or hydrogen forms
-more the reactive an element the more it likes to stay as ions so if a metal is more reactive than hydrogen, it stays as ions and hydrogen bubbles off
-if metal is less reactive than metal forms

Question 8

rules for electrolysis of a solution: ANODE

Answer 8

a non-metal other than hydrogen forms
-if its a concentrated solution of a halide (Cl-,Br-,I-) then chlorine, bromine or iodine form
-if the halide solution is dilute or there is no halide then oxygen forms

Question 9

RAC

Answer 9

reduction at cathode so gain of electrons at cathode

Question 10

Half equation for electrode reactions

Answer 10

1 name the ions present and the products
2. write each half equation correctly (positive ion at cathode, negative at anode)
3, add state symbols

Question 11

electroplating

Answer 11

using electricity to coat one metal with another
cathode - obj to be electroplated
anode - metal X
electrolyte - a solution of a soluble compound of X