chemical changes

Question 1

what colour is strong acid with examples

Answer 1

Deep red
car battery acid, hydrochloric acid

Question 2

what colour is weaker acid with examples?

Answer 2

Acid/normal rain
Lighter Orange/yellow

Question 3

what colour is water on a pH scale

Answer 3

Green

Question 4

what colour is a weaker alkaline? With examples.

Answer 4

Blue to weaker indigo
Washing up liquid, pancreatic juice

Question 5

What colour are stronger acids with examples?

Answer 5

Violet and deep pink
Bleach, caustic soda

Question 6

what is the equipment called that measures pH?

Answer 6

Universal indicator

Question 7

What ions do acids and alkaline molecules release in aqueous solutions

Answer 7

Acid: H+
Alkali: OH-

Question 8

what is a base?

Answer 8

Any substance that will react with an acid to form a salt

Question 9

what is neutralisation and how is it showing in an equation?

Answer 9

Neutralisation is the reaction between acids and bases
Acid + base —> salt + water

Question 10

What do titrations do?

Answer 10

allow you to find out concentrations needed neutralisation

Question 11

How do you do a titration?

Answer 11

PIPFRACRU
say you want to find out the concentration of some alkali
• pippet to add a 25cm cubed of the alkaline to a conical flask
• indicator – five drops
• place on white tile so colour change can be observed
• Funnel to fill a burette with acid of a known concentration - below eye level
• record initial volume in burette
• Add bit by bit, occasionally swirling flask
• Changed colour of indicator when all alkali has been neutralised
• record final of acid in the burette
• Use initial reading to calculate volume of acid used to neutralise
• repeat two more times to find an average

Question 12

What is a strong acid with three examples?

Answer 12

strong acids ionised completely in aqueous solutions
Sulphur, hydrochloric, nitric

Question 13

What is a weak acid, with three examples?

Answer 13

Partially ionise in aqueous solutions
Ethanolic, citric, carbonic

Question 14

What is the pH of an acid or alkaline? What is the pattern?

Answer 14

Measure of concentration of H+ ions in solution
stronger acids have a lower pH, as they fully ionise, producing greater concentration of H+

Question 15

relationship between pH scale and concentration of H+ ions

Answer 15

as pH scale decreases by one unit unit, concentration of H+ ions increases by 10 times

Question 16

concentration of H+ difference between pH 1 and pH 2

Answer 16

10x

Question 17

concentration of H+ ions between pH 1 and pH 3

Answer 17

100x

Question 18

What is concentration of acid?

Answer 18

Amount of acid molecules in a given volume of solution

Question 19

Acid strength versus acid concentration

Answer 19

Strength tells you proportion of acid molecules that will ionise
Concentration tells you amount of acid molecules in given volume

Question 20

equation for acid+ metal oxide AND acid + metal hydroxide

Answer 20

acid + metal oxide/hydroxide —> salt + water

Question 21

equation for acid + metal carbonate

Answer 21

Acid + metal carbonate —> salt + water + carbon dioxide

Question 22

how can you make copper sulphate crystals using copper oxide and sulphuric acid

Answer 22

• gently heat the acid until small bubbles visible
• add small amount of oxide using spatula and stir
• continue adding until excess can be seen, which ensures all the acid has reacted
• using filter funnel and filter paper, use filtration to remove excess, leaving copper sulphate solution
• heat in evaporating basin over boiling water, until half of solution remains
• leave for 24 hours for crystals to form
• pat dry with paper towels

Question 23

three examples of indicators you can use in titrations , their colour change (acid —> alkali)

Answer 23

phenolphthalein: colourless -> pink
litmus: red -> blue
methyl orange: red -> yellow

Question 24

How is reactivity determined in metals and why?

Answer 24

How easily they lose electrons -
When they react, they lose electrons and form positive ions

Question 25

how to remember the reactivity series

Answer 25

people say little children may cause zesty inmates happy cocks

Question 26

what is the reactivity series

Answer 26

potassium
sodium
Lithium
Calcium
Magnesium
Carbon
Zinc
Iron
Hydrogen
Copper

Question 27

How is the speed of a reaction indicated?

Answer 27

Rate of bubbles

Question 28

oxidation versus reduction

Answer 28

Oxidation is gain of oxygen
(+ loss of electrons)

Reduction is loss of oxygen
(+ gain of electrons)

Question 29

which metals need to be extracted by electrolysis and which by reduction with carbon?

Answer 29

Above carbon: electrolysis
Below carbon: reduction with carbon

Question 30

What is a redox reaction?

Answer 30

Reduction and oxidation happening at the same time

Question 31

step of displacement redox reactions

Answer 31

• remove particles that do not change (same on both sides) called ionic equation
• split into two half equations
• add in electrons

Question 32

How is electric current passed in electrolysis?

Answer 32

Through an electrolyte, which must be molten or dissolved so that ions are free to move

Question 33

where do positive ions go in the electrolyte and where do negative irons go?

Answer 33

Positive go to cathode to gain electrons (reduction) H+ ions also

negative go to anode to lose electrons (oxidisation) OH- ions also

Question 34

how do you predict what products you will get at the cathode?

Answer 34

If the metal is more reactive than hydrogen, hydrogen (H2) is produced
If it is less reactive, pure metal is produced

Question 35

How do you predict what products you will get at the anode?

Answer 35

if a halide ion is present, the halogen will be produced
if halide ion is not present, oxygen and water is produced