C5 (Chemical Changes)

Question 1

PH Scale

Answer 1

0 to 6 are acids
7 is neutral
8-14 are alkalis

Question 2

2 ways measure PH

Answer 2

• indicator that is a dye with a colour change

- PH probe that is more accurate

Question 3

Acid definition

Answer 3

A substance with a PH less that 7 and is an aqueous solution, with H+ ions forming in water

Question 4

Base definition

Answer 4

Substance with PH greater than 7

Question 5

Alkali definition

Answer 5

This is a base that dissolves in water go form a solution with PH greater than 7 and form OH- ions in water

Question 6

Acid + base ->

Answer 6

Salt + water

Question 7

5 Stages of Titration Practical

Answer 7

1) Add the alkali to a conical flask with a pipette with a few drops of indicator
2) use a funnel to fill burette with a known concentration acid until it reaches eye level
3) Slowly add the acid to the alkali to find the exact point of the colour change when it is neutralised
4) find the point of neutralisation and find the volume of acid needed to neutralise
5) 1st should be rough so repeat few times for concordant results

Question 8

Colour change for litmus

Answer 8

Red acid

Blue alkalis

Question 9

Colour change for methyl orange

Answer 9

Red acid

Yellow alkali

Question 10

Colour change for phenolphthalein

Answer 10

Colourless acid

Red pink alkali

Question 11

Strong Acids

Answer 11

• ionise completely in water, meaning all particles dissociate to release H+ ions
• more reactive than weak as the conc of H+ ions is higher

Question 12

Weak Acid

Answer 12

• do not fully ionise and only small proportion of H+ ions dissociate
• reversible reaction between undissociated and dissociated with position of equilibrium more to left

Question 13

General rule for H+ ion concentration change

Answer 13

Factor of H+ ion concentration changes by = 10^x

Question 14

Acid + metal oxide ->

Answer 14

Salt + water

Question 15

Acid + Metal Hydroxide ->

Answer 15

Salt + water

Question 16

Acid + Metal Carbonate ->

Answer 16

Salt + water + Carbon Dioxide

Question 17

Order of the reactivity series

Answer 17

Potassium, sodium, lithium, calcium, magnesium, (carbon), Zinc, Iron, (Hydrogen), Copper

Question 18

How is reactivity series determined

Answer 18

• how east metals loose electrons to form positive ions

- easiest (most reactive) at top and hardest (least reactive) at bottom

Question 19

Acid + metal ->

Answer 19

Salt + hydrogen

Question 20

Metal + Water ->

Answer 20

Metal Hydroxide + Hydrogen

Question 21

How to extract metals using the reactivity series

Answer 21

• above carbon use electrolysis

- below carbon use reduction using carbon

Question 22

Formation of metal ore and extraction of metal

Answer 22

• for metal ore it is oxidised = gain of O2

- for extraction of metal it is reduction= loss of O2

Question 23

Displacement Reaction definition

Answer 23

A more reactive metal will displace a less reactive metal from it’s compound

Question 24

Redox Reaction

Answer 24

Where reduction and and oxidation occur simultaneously