Chemical Reactions

Question 1

what is formed when a metal reacts with oxygen?

Answer 1

a metal oxide

Question 2

define oxidation

Answer 2

gaining oxygen, losing electrons

when a metal becomes a metal oxide, it has gained oxygen and become oxidised

Question 3

define reduction

Answer 3

losing oxygen, gaining electrons

Question 4

when a metal reacts with water, what are the products?

Answer 4

a metal hydroxide + hydrogen

Question 5

what does the reactivity of a metal depend on?

Answer 5

it’s ability to lose electrons and form a positive ion

Question 6

how do we extract metals that have formed a compound with oxygen?

Answer 6

use a more reactive element/metal to displace it from the compound

Question 7

which ion does an acid produce in aqueous solutions?

Answer 7

H+ ions

Question 8

what are bases?
(2)

Answer 8

• chemicals that can neutralise acids, producing a salt and water
• usually metal oxides or metal hydroxides

Question 9

what are alkalis?

Answer 9

bases that are soluble in water

Question 10

which ions do alkalis produces in aqueous solutions?

Answer 10

OH- ions

Question 11

how can we determine the ph of a solution?

Answer 11

• ph probe
  determines it electronically
• universal indicator
  changes colour depending on the acidity/alkilinity of a solution

Question 12

what is the word equation for an acid and a metal reacting?

Answer 12

acid + metal&raquo_space;»> salt + hydrogen

Question 13

what is the word equation for reacting an acid with a base or an alkali?

Answer 13

acid + base/alkali&raquo_space;»> salt + water

Question 14

what is the word equation for when an acid reacts with a metal carbonate

Answer 14

acid + metal carbonate&raquo_space;»» salt + water + carbon dioxide

Question 15

what is a strong acid?
examples?

Answer 15

fully ionise to release H+ ions in aqueous solutions

• hydrochloric acid
• sulfuric acid
• nitric acid

Question 16

what is a weak acid?

Answer 16

only partially ionise to release H+ ions in aqueos solutions

• carbonic acid
• ethanoic acid
• citric acid

Question 17

define electrolysis

Answer 17

using electricity to split up ionic compounds

Question 18

why does the ionic compound have to be molten or dissolved?

Answer 18

electrolysis can not be carried out on a solid because the ions aren’t free to move.

if you want to split the compound, you need to be able to split the two ions that make it up

Question 19

what is the positive electrode called?
what is the negative electrode called?

Answer 19

• anode
• cathode

Question 20

what will be produced at the cathode in an aqueous solution?

Answer 20

if the metal is more reactive than hydrogen, hydrogen will be produced at the cathode

if not, the metal will be produced

Question 21

what will be produced at the anode in an aqueous solution?

Answer 21

if a halide ion is present within the aqueous solution, then the halogen will be produced

if not, oxygen will be given off

Question 22

how is aluminium extracted from aluminium oxide by electrolysis? (3)

Answer 22

• aluminium oxide is mixed with cryolite to lower the melting point
• this reduces the amount of energy needed and saves money
• aluminium oxide is now molten

Question 23

what is an exothermic reaction?

Answer 23

• transfers energy to the surroundings
• temperature of the surroundings increases
• reactants have more energy
• products have less energy

Question 24

what is an endothermic reaction?

Answer 24

• takes in energy from the surroundings
• temperature of the surroundings decreases
• reactants have less energy
• products have more energy

Question 25

examples of exothermic reactions:

Answer 25

• hand warmers
• self heating cans
• combustion

Question 26

example of endothermic reactions:

Answer 26

thermal decomposition

Question 27

define activation energy

Answer 27

the minimum amount of energy that particles need in order to react