C4- Chemical Changes

Question 1

What does the pH Scale show

Answer 1

Lower pH- more acidic, higher pH- more alkaline

Question 2

Neutralisation

Answer 2

Reaction between acids and bases

Question 3

Neutralisation between acids and alkalis

Answer 3

H+ + Oh- - >H20

Question 4

Strong acids

Answer 4

Ionise completely in water

Question 5

Weak acids

Answer 5

Do not ionise fully in solution

Question 6

Strong acids and weak acids rate of reaction

Answer 6

Strong acids more reactive than weak acids of the same concentration

Question 7

What is pH

Answer 7

pH is a measure of the concentration of hydrogen ions in the solution, for every decrease of 1 on the pH scale the concentration of hydrogen ions increase by a factor of 10

Question 8

Reaction of acids with metal oxides and hydroxides

Answer 8

All reactions form a salt and water

Question 9

Acids and metal carbonates

Answer 9

Produce salt, water and carbon dioxide

Question 10

Make soluble salts using insoluble base (rp)

Answer 10

1. Gently warm dilute acid using bunsen burner, then turn off bunsen burner
2. Add the insoluble base to the acid a bit at a time until no more reatcs
3. Filter out the excess to get the salt solution
4. For pure crystals of salt, gently heat in water bath to evaporate water then leave to cool. Crystals should form this is called crystallisation

Question 11

The reactvity series

Answer 11

The higher a metal is in the reactivity series the more easily if reacts water or acid

Question 12

Metals react with acids

Answer 12

Produce salt and hydrogen gas, the speed of reaction is indicated by rate hydrogen bubbles are given off, the more reactive the faster

Question 13

Metals react with water

Answer 13

Metal + water -> metal hydroxide + hydrogen

Question 14

Reduction reaction

Answer 14

Reaction that seperates a metal from its oxide

Question 15

Oxidation

Answer 15

Gain of oxygen

Question 16

Reduction

Answer 16

Loss of oxygen

Question 17

How position of metal in reactivity series determines whether it can be extracted by reaction with carbon

Answer 17

Metals higher than carbon have to be extracted by electrolysis (expensive), metals below carbon can be extracted by reduction using carbon because carbon can only take the oxygen away from metals which are less reactive

Question 18

Oxidation and radiation in terms of electrons

Answer 18

Oxidation- loss of electrons
Reductiom- gain of elctrons
OIL RIG

Question 19

Redox reactions

Answer 19

Reduction and oxidation at the same time

Question 20

Displacement reaction

Answer 20

One metal kicking another out. A more reactive metal will displace a less reactive metal from its compound

Question 21

What happens in displacement reactions

Answer 21

Metal ion gain electrons and is reduced. The metal atom always loses electrons and is oxidised

Question 22

Ionic equation

Answer 22

The particles that react and the products they form are shown

Question 23

Electrolysis

Answer 23

Splitting up with electricity

Question 24

What happens during electrolysis

Answer 24

1. An electric current is passed through an electrolyte. The ion moves towards the elctrodes where they react and the compound decomposes
2. The positive ions move towards the cathode and gain electrons
3. Negative ions move towards anode and lose electrons
4. Creates flow of charged
5. As ions gain or lose electrons, they form the uncharged element and are discharged from electrolyte

Question 25

Electrolysis of molten ionic solids

Answer 25

Ionic solids cant be electrolysed as they are in fixed positions but molten ionic compounds can be eletrolysed because ions can move freely and conduct electricity

Question 26

How metals more reactive to be reduced with carbon can use electrolysis to extract it

Answer 26

1. Aluminium extracted form ore of bauxite by electrolysis (contains aluminium oxide)
2. Aluminium oxide very high melting point so mixed with cryolite to lower melting point
3. Positive aluminium ions attracted to negative electrode where they pick up three electrons and turn into neutral ions aluminium atoms which sink into bottom of electrolysis tank
4. Negative O2- ions are attracted to the positive electrode where they lose two electrons. The neutral oxygen atoms then combine with 02 molecules

Question 27

Electrolysis of aqueous solutions

Answer 27

1. In aqueous solutions, as well as ions from ionic compounds, there will be hydrogen ions and hydroxide ions from water
2. At the cathode If h+ ions and metal ions are present hydrogen gas will be produced
3. If elemental metal is more reactive than hydrogen. The metal ions form an elemental metal that is less reactive than hydrogen, a solid layer of the pure metal will be produced instead
4. At the anode if OH- and halide ions are present, molecultes of chrlorine, bromien or iodine will be formed. If no halide ions are prsent, the the OH- ions are discharged and oxygen will be formed

Question 28

Half equations

Answer 28

When combining half equations the number of electrons needs to be the same for each half equation