Chemical Change

Question 1

what are wide range indicators

Answer 1

contain a mixture of dyes that gradually change colour over a range of ph

Question 2

how are ph probes used

Answer 2

probe attached to meter and probe in solution you are measuring. more arcuate as you get a number

Question 3

what happens if you dissolve an acid in water

Answer 3

hydrogen ions will be formed (H+)

Question 4

what happens to alkali if you dissolve it in water

Answer 4

hydroxide ions form (OH-)

Question 5

what is the general formula for a neutralisation reaction

Answer 5

acid + alkali = salt + water

Question 6

during neutralization reactions hydrogen ions and hydroxide ions react to form what

Answer 6

water

Question 7

what is a titration

Answer 7

an experiment that lets you see what volume of reactant is needed to completely react with another reactant

Question 8

what is universal indicator

Answer 8

used to estimate ph of solution. thr colour gradually changes. cantuse in titration cus colour change is too gradual

Question 9

what indicators could be used in a titration and why

Answer 9

phenolphthalein, methyl orange and litmus

they are single indicators meaning they have one distinct colour change

Question 10

what is the colour change in phenolphthalein

Answer 10

pink in alkalis colourless in acid

Question 11

what is the colour change in methyl orange

Answer 11

yellow in alkalis red in acids

Question 12

what is the colour change in litmus

Answer 12

blue in alkalis red in acids

Question 13

what does the strength of an acid tell you

Answer 13

the proportion of acid particles that will dissociate to produce H+ ions in a solution. high proportion = high strength

Question 14

why are strong acids more reactive than weak acids

Answer 14

reactions of acids involve H+ ions reacting w other substances so if the concentration of H+ ions is higher then the rate of reaction will be faster

Question 15

what is the relation between the ph scale and the concentration of H+ ions

Answer 15

for every decrease of 1 the concentration of h+ ions increase by a factor of 10

Question 16

how does concentration effect the ph of an acid

Answer 16

if the acid has been watered down then the amount of h+ ions will be proportionally smaller so the ph will increase even though the acid maybe a strong acid

Question 17

what are bases

Answer 17

substances that can react with acids in neutralization reactions. all metal oxides and hydroxides are bases

Question 18

why are soluble metal hydroxides alkalis

Answer 18

disolve in water to produce OH- ions

Question 19

what is the general equation for the reaction of metal oxides or metal hydroxides with acids

Answer 19

they make salt and water

Question 20

hydrochloric acid + copper oxide =

Answer 20

copper chloride + water

Question 21

what do reactions with hydrochloric acid, sulphic acid and nitric acid give in the name

Answer 21

chlorides
sulphates
nitrates

Question 22

list the reactivity series

Answer 22

potassium sodium lithium calcium mafnesuim carbon zinc iron hydrogen copper

Question 23

how can you test the reactivity of metals

Answer 23

measure temp change in reaction

react w metal and monitor rate of hydrogen produced

Question 24

acid + metal =

Answer 24

salt and hydrogen

Question 25

how can hydrogen be detected

Answer 25

lit splint in mouth of tube . makes squeaky pop

Question 26

metal + water =

Answer 26

metal hydroxide + hydrogen

Question 27

what is a metal ore

Answer 27

rock containing enough of the metal to make it profitable to extract

Question 28

what is oxidation

Answer 28

gain of oxygen.

Question 29

what is reduction

Answer 29

loss of oxygen

Question 30

how are metals less reactive than carbon extracted from their ores

Answer 30

reducing it n a reaction with carbon. Oxygen is removed from ore and the carbon gains it so the carbon is oxidized. displacement.

Question 31

how are metals more reactive than carbon extracted from their ores

Answer 31

electrolysis

Question 32

what is a redox reaction

Answer 32

oxidation and reduction occurs at the same time

Question 33

what happens in terms of electrons in oxidation and reduction

Answer 33

oxidation - loss of electrons | reduction - gain of electrons

Question 34

why are displacement reactions redox

Answer 34

metal ion is being reduced and metal atom is being oxidised

Question 35

what is an electrolyte

Answer 35

liquid in electrolysis that conducts electricity. They contain free ionns and are usally a molton or disolved ionic substance e.g sodium chloride

Question 36

what is an electrode

Answer 36

solid that conducts electricity that is submerged in electrolyte. ions move from one elecrode to the other which is what compleates the circuit

Question 37

where do the positive ions more to in electrolysis

Answer 37

cathode (negative electrode) and gain electrons

Question 38

where do the negative ions move to in electrolysis

Answer 38

the anode (positive electrode) and lose electrons

Question 39

what happens after an ion gains or losses electrons in electrolysis

Answer 39

becomes atom or molecule and is released

Question 40

what are binary compounds

Answer 40

ionic compounds containing two elements that are ions - a positive metal ion and a negative metal non ion

Question 41

what do half equations show in electrolysis

Answer 41

show the reactions at the electrodes

Question 42

how do you draw a half equation for electrolysis

Answer 42

on the left hand side of the equation, draw the symbol for the positive ion write the symbol for the neutral molecule on the right hand side of the equation balance number of atoms in the equation balence the charges by adding or subtacting electons shown as e- this works for at the cathode. for writing one forthe anode , the negitive ion needs to be on the right hand side

Question 43

what can bauxite be purified to make

Answer 43

aluminium oxide (Al2O3)

Question 44

is is aluminon oxide dissolved in molten cryolite

Answer 44

brings melting point from 200 to 900

Question 45

what material could be used as an electrode

Answer 45

carbon (graphite)

Question 46

in the electrolysis of aluminon oxide, why do the electrodes have to be sometimes replaced

Answer 46

oxygen loses electrons at positive electrode making neutral O2 whick react w the carbon and form co2

Question 47

at the negative electrode what would happen if a h+ ion and metal ion is present when the metal is more reactive than the hydrogen

Answer 47

the more reactive element is more likely to stay as an ion so hydrogen will be produced and the metal will remain as an ion

Question 48

if OH- is at the positive electrode but not any halide ions what will happen

Answer 48

OH- ions are discharged and oxygen and water will be formed