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Chemistry > Chemical Change > Flashcards

Chemical Change Flashcards

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1
Q

what are wide range indicators

A

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

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2
Q

how are ph probes used

A

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

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3
Q

what happens if you dissolve an acid in water

A

hydrogen ions will be formed (H+)

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4
Q

what happens to alkali if you dissolve it in water

A

hydroxide ions form (OH-)

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5
Q

what is the general formula for a neutralisation reaction

A

acid + alkali = salt + water

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6
Q

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

A

water

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7
Q

what is a titration

A

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

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8
Q

what is universal indicator

A

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

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9
Q

what indicators could be used in a titration and why

A

phenolphthalein, methyl orange and litmus

they are single indicators meaning they have one distinct colour change

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10
Q

what is the colour change in phenolphthalein

A

pink in alkalis colourless in acid

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11
Q

what is the colour change in methyl orange

A

yellow in alkalis red in acids

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12
Q

what is the colour change in litmus

A

blue in alkalis red in acids

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13
Q

what does the strength of an acid tell you

A

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

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14
Q

why are strong acids more reactive than weak acids

A

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

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15
Q

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

A

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

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16
Q

how does concentration effect the ph of an acid

A

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

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17
Q

what are bases

A

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

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18
Q

why are soluble metal hydroxides alkalis

A

disolve in water to produce OH- ions

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19
Q

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

A

they make salt and water

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20
Q

hydrochloric acid + copper oxide =

A

copper chloride + water

21
Q

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

A

chlorides
sulphates
nitrates

22
Q

list the reactivity series

A

potassium sodium lithium calcium mafnesuim carbon zinc iron hydrogen copper

23
Q

how can you test the reactivity of metals

A

measure temp change in reaction

react w metal and monitor rate of hydrogen produced

24
Q

acid + metal =

A

salt and hydrogen

25
Q

how can hydrogen be detected

A

lit splint in mouth of tube . makes squeaky pop

26
Q

metal + water =

A

metal hydroxide + hydrogen

27
Q

what is a metal ore

A

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

28
Q

what is oxidation

A

gain of oxygen.

29
Q

what is reduction

A

loss of oxygen

30
Q

how are metals less reactive than carbon extracted from their ores

A

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

31
Q

how are metals more reactive than carbon extracted from their ores

A

electrolysis

32
Q

what is a redox reaction

A

oxidation and reduction occurs at the same time

33
Q

what happens in terms of electrons in oxidation and reduction

A

oxidation - loss of electrons

reduction - gain of electrons

34
Q

why are displacement reactions redox

A

metal ion is being reduced and metal atom is being oxidised

35
Q

what is an electrolyte

A

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

e.g sodium chloride

36
Q

what is an electrode

A

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

37
Q

where do the positive ions more to in electrolysis

A

cathode (negative electrode) and gain electrons

38
Q

where do the negative ions move to in electrolysis

A

the anode (positive electrode) and lose electrons

39
Q

what happens after an ion gains or losses electrons in electrolysis

A

becomes atom or molecule and is released

40
Q

what are binary compounds

A

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

41
Q

what do half equations show in electrolysis

A

show the reactions at the electrodes

42
Q

how do you draw a half equation for electrolysis

A

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

43
Q

what can bauxite be purified to make

A

aluminium oxide (Al2O3)

44
Q

is is aluminon oxide dissolved in molten cryolite

A

brings melting point from 200 to 900

45
Q

what material could be used as an electrode

A

carbon (graphite)

46
Q

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

A

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

47
Q

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

A

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

48
Q

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

A

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

Chemistry (15 decks)

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