C-4 Chemical changes

Question 1

• What are acids

Answer 1

• Produce hydrogen ions in aqueous solutions

- Ph less than 7

Question 2

What are alkalis

Answer 2

• Aqueous solutions of alkalis contain hydrogen oxides

- Ph more than 7

Question 3

How can PH be measured

Answer 3

• Is the measure of acidity or alkalinity
• Measured using universal indicator or PH probe
• PH probe- electronic
• Indicator- dyes

Question 4

What happens in neutralisation in acids and bases

Answer 4

• Hydrogen ions react with hydroxide ions to produce water
• Neutralisation0 acid + base – salt + water

H+ + OH- – H2O (I)

Question 5

• What is a strong acid

Answer 5

• Completely ionised in aqueous solution
• All acid particles dissociate
• Hydrochloric, nitric and sulphuric
• faster reactions

Question 6

What is a weak acid

Answer 6

• Do not fully ionise, in aqueous solutions

- Ethanoic, citric and carbonic

Question 7

What effect does concentration have on strength of acid

Answer 7

• The higher the concentration, the stronger the Ph

- As Ph decreases by 1, hydrogen ion concentration increases by factor of 10

Question 8

• What do acids do with metals

Answer 8

• Acids react with some metals to produce salts an hydrogen

Question 9

What is a redox reaction

Answer 9

• Redox reactions are displacement reactions
• A more reactive metal will displace a less reactive
• Always metal own that gains electrons

Question 10

What are alkalis

Answer 10

• Bases that dissolve water

Question 11

• What do metal oxides and metal hydroxides and react with water to make

Answer 11

• Form a salt and water

Question 12

What do acids and metal carbonates produce

Answer 12

• Metal carbonates are bases

- react with acids to product salts

Question 13

How are soluble salts made

Answer 13

• Using insoluble base
• Pick right acid and base
• Warm flute acid on burner then turn off
• Add insoluble base bit at a time, tunnel none reacts.
• Filter out excess solid
• Warm using water bath or heater ti evaporate water, cool. Crystals form

Question 14

What is the reactivity series

Answer 14

• Metals in order of reactivity
• how easily they lose electrons
• Higher up, faster and easier it reacts with water

Question 15

What is the order in reactivity series

Answer 15

• Potassium
• Sodium
• Lithium
• Calcium
• Magnesium
• Carbon
• Zinc
• Iron
• Hydrogen
• Carbon

Question 16

What does how metals react tell you about reactivity

Answer 16

More reactive means faster the rate.

Question 17

What is metal extraction

Answer 17

• Lots of metals react with oxygen to make oxides
• Oxidiation
• Form ores

Question 18

How does metal extraction take place from ores

Answer 18

• Reduction reaction

Question 19

What is a formation of ore reaction

Answer 19

• Oxidation
• 2MG + O2 - 2MGO
• Magnesium

Question 20

What is the formulation for extraction of metal from ore

Answer 20

• Reduction
• Copper

2CuO + C – 2Cu + CO2

Question 21

How can metals be extracted buy carbon use

Answer 21

• Chemical
• Some metals
• Carbon gains the oxygen that is lost from reduction

e.g - iron

2Fe2O3 + 3C – 4Fe + 3CO2

Question 22

What determines wether or not a metal can be extracted by carbon

Answer 22

If its less reactive than carbon so it can displace it

- If not electrolysis is used

Question 23

What does electrolysis mean

Answer 23

• Splitting up with electrolysis

Question 24

• What happens within electrolysis

Answer 24

• Electrical current is passed through molten for dissolved ionic compound
• Positive ions move towards cathode - gain electrons - reduced
• Negative ions, move towards anode - lose electrons oxides

Question 25

How can electrolysis be used to extract ores

Answer 25

• Expensive
• Molten
• Sperated