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Chemisty > Acids > Flashcards

Acids Flashcards

1
Q

what is the range on the pH scale?

A

0 to about 14

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2
Q

what does the pH scale tell you about a solution?

A

how acidic or alkaline it is

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3
Q

what number on the pH scale is neutral?

A

7

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4
Q

what number is most acidic on the pH scale?

A

0

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5
Q

what number is most alkaline on the pH scale?

A

14

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6
Q

what is a universal indicator made from and how does this work?

A

made from a mixture of dyes that change colour in a gradual way over a range pH

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7
Q

what is the most common form of universal indicator? how does it work? how accurate is it?

A

known as a wide range indicator

changes through a variety of colours from pH 1 to pH 14

it is not very accurate

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8
Q

when testing with a universal indicator, what do you do with the colour of the paper of soultion?

A

check it against a chart to find the correct pH

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9
Q

what is a more accurate way than a universal indicator to measure the pH?

A

a pH meter

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10
Q

what is a common indicator?

A

litmus

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11
Q

what can be used as an indicator?

A

any substance that has more than one colour form depending on the pH

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12
Q

what colour is litmus in acidic solution?

A

red

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13
Q

what colour is litmus in alkaline solution?

A

blue

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14
Q

what colour is litmus in neutral solution?

A

purple

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15
Q

what colour is methyl orange in alkaline solutions?

A

yellow

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16
Q

what colour is methyl orange in acidic solutions?

A

red

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17
Q

what colour is phenolphthalien in alkaline solutions?

A

bright pink

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18
Q

what colour is phenolphthalien in acidic solutions?

A

colourless

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19
Q

what is an acid-base indicator?

A

chemicals that change to a different colour when the pH of a solution changes

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20
Q

what colour is universal indicator in acidic solution?

A

strong red

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21
Q

what colour is universal indicator in alkaline solution?

A

strong blue

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22
Q

why is universal indicator the best indicator?

A

a range of colour of pH

you can see how strongly acidic or alkaline a solution is

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23
Q

what does the pH show us?

A

the concentration of hydrogen ions in a solution compared to distilled water

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24
Q

strong alkalines have … H+ ions

A

strong alkalines have very few H+ ions

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25
Q

strong acids have … H+ ions

A

strong acids have many H+ ions

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26
Q

what type of reaction is neutralisation?

A

exothermic

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27
Q

what is an acid?

A

a substance that, when dissolved in water, releases hydrogen H+ ions

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28
Q

what does dissociate mean?

A

to break apart

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29
Q

if an acid fully dissociates it is a … acid

A

if an acid fully dissociates it is a strong acid

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30
Q

if an acid partly dissociates it is a … acid

A

if an acid partly dissociates it is a weak acid

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31
Q

what is an alkali?

A

a base that can dissole in water

when dissolved in water, releases an OH- ion

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32
Q

what can alkalis do to acids?

A

neutralise them

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33
Q

what are bases?

A

substances that combine with hydrogen ions

react with acids to form a salt and water (and sometimes carbon dioxide as well)

usually metal oxides

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34
Q

what can bases do to acids?

A

neutralise them

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35
Q

do bases release a hydroxide ion when dissolved in water? why?

A

no

they do not dissolve in water

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36
Q

what do alkalis release when they fully dissociate?

A

hydroxide ions

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37
Q

what do alkalis release when they partly dissociate?

A

(less) hydroxide ions

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38
Q

are all alkalis bases or are all bases alkalis?

A

all alkalis are bases

not all bases are alkalis

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39
Q

what is formed when an acid reacts with an alkali? what is the balanced and ionic equation for this?

A

water

hydrogen + hydroxide —> water

H+ (aq) + OH- (aq) —> H2O (l)

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40
Q

metals below hydrogen in the reactivity series … with dilute acids

A

metals below hydrogen in the reactivity series don’t react with dilute acids

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41
Q

metals above hydrogen in the reactivity series … with dilute acids

A

metals above hydrogen series react with dilute acids

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42
Q

the higher the metal in the reactivity series, the more … the reaction with an acid

A

the higher the metal in the reactivity series, the more vigorous the reaction with an acid

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43
Q

why would you never mix metals such as sodium or potassium with acids?

A

the reaction would be too vigorous

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44
Q

what is the summary equation for metals reacticing with acids?

A

acid (aq) + metal (s) —> salt (aq) + hyrogen (g)

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45
Q

what happens during a reaction between a metal and an acid?

A

the metal displaces the hydrogen ion from the acids which is then liberated as hydrogen gas molecules

the metal combnes with the non-metal of the acid to form a salt

the metal ionises

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46
Q

what salts are formed from the parent acid sulphuric acid?

A

sulphates

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47
Q

what salts are formed from the parent acid hydrochloric acid?

A

chlorides

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48
Q

what salts are formed from the parent acid nitric acid?

A

nitrates

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49
Q

what happens when you react magnesium with dilute sulphuric acid?

A

there is rapid fizzing and a colourless gas is evolved

this gas squekily pops when tested with a lighted splint (the test for hydrogen)

the reaction mixture gets very warm as heat is produced

the magnesium gradually disappears to leave a colourless solution of magnesium sulphate

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50
Q

what is the balanced equation for the reaction of magnesium with dilute sulphuric acid?

A

Mg(s) + H2SO4 (aq) —> MgSO4 (aq) + H2 (g)

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51
Q

what is the kind of reaction is the reaction of magnesium with dilute sulphuric acid? explain this breifly

A

a displacement reaction

the more reactive magnesium has displaced the less reactive hydrogen

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52
Q

what happens when you react magnesium with dilute hydrochloric acid?

A

there is rapid fizzing and a colourless gas is evolved

this gas squekily pops when tested with a lighted splint (the test for hydrogen)

the reaction mixture gets very warm as heat is produced

the magnesium gradually disappears to leave a coloourless solution of magnesium chloride

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53
Q

what is the equation for the reaction of magnesium with dilute hydrochloric acid?

A

Mg(s) + 2HCl(aq) —> MgCl2 (aq) + H2 (g)

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54
Q

all acids in solution contain … ions

this means that magensium will react with any simple dilute acid in … way

A

all acids in solution contain hyrogen ions

this means that magensium will react with any simple dilute acid in the same way

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55
Q

the reaction of zinc with simple dilute acids is … than magnesium as zinc is … on the reactivity series

A

the reaction of zinc with simple dilute acids is slower than magnesium as zinc is lower on the reactivity series

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56
Q

how can the reaction of zinc with simple dilute acids be sped up?

A

if the reaction is heated or if the zinc is impure

a little copper(II) sulphate solution is often added to these reactions to make the zinc impure

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57
Q

how is hydrogen often made in the lab?

A

usually from zinc and dilute sulphuric acid, with a very small amount of copper(II) sulphate solution added to speed up the reaction (this is not a catalyst as it is used up in the reaction)

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58
Q

how do you test for hydrogen?

A

hyrdogen reacts with oxygen in the presence of a flame or a spark to give water

a lighted splint placed at the mouth of a test tube of hydrogen will give a squeaky pop as the hydrogen reacts with oxygen in the air

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59
Q

what do most reactions between acids and metal oxides need? why?

A

heat to get the reaction started

60
Q

what colour is copper (II) sulphate?

A

blue

61
Q

what is the summary equation for acids and metal oxides?

A

acid(aq) + metal oxide(s) —> salt(aq) + water(l)

62
Q

what happens during a reaction with an acid and a metal oxide?

A

the metal displaces the hydrogen ion which reacts with the oxide ion to form water

the metal combines with the non-metal of the acid to dorm a salt

the metal ionises

63
Q

what is the summary equation for the reacting acids and metal hydroxides (alkali)?

A

acid(aq) + metal hyrdoxide(aq) —> salt(aq) + water(l)

64
Q

what happens during a reaction between an acid and a metal hydroxide?

A

the metal displaces the hydrogen ion which reacts with the hydroxide ion to form water

the metal ion combines with the non-metal ion of the acid to form a salt

65
Q

do all metal hydroxides react with acids?

A

yes

66
Q

solutions of soluble base are (alkaline/acidic) and have a pH of (greater/lower) than 7

A

solutions of soluble base are alkaline and have a pH of greater than 7

67
Q

how can you tell excatly when enough acid has been added to an alkali to produce a neutral solution as everything involved is colourless?

A

use an indicator: methyl orange

the alkali is neutralised when the solution shows the first trace of orange

if it turns red you have added too much acid

68
Q

around what pH does methyl orange change colour?

A

pH 4

69
Q

carbonates react with cold dilute acids to produce …

A

carbonates react with cold dilute acids to produce carbon dioxide

70
Q

what is the summary equation for acids and carbonates?

A

acid(aq) + metal carbonate(s) —> salt(aq) + water(l) +carbon dioxide(g)

71
Q

what happens during a reaction between an acid and a metal carbonate?

A

the metal displaces the hydrogen ion which reacts with the carbonate ion to form water and carbon dioxide

the metal combines with the non-metal of the acid to form a salt

72
Q

what does carbon dioxide do to lime water?

A

turns it milky

73
Q

an acid is a proton (hydrogen ion) …

A

an acid is a proton (hydrogen ion) donor

74
Q

a base is a proton (hydrogen ion) …

A

a base is a proton (hydrogen ion) acceptor

75
Q

what are salts?

A

ionic substances formed when acids react with bases

76
Q

what are some common acids (6)?

A

sulphuric acid H2SO4

hydrochloric acid HCl

nitric acid HNO3

phosphoric acid H3PO4

ethanoic acid C2H4O2

tartaric acid C4H6O6

77
Q

what are some common bases (3)?

A

metal oxides

metal hydroxides

metal carbonates

78
Q

what are some common alkalis (1) and water soluble metal hydroxides (3)?

A

common alkalis:

ammonia NH3

common water soluble metal hydroxides:

sodium hydroxide NaOH

potassium hydroxide KOH

calcium hydroxide Ca(OH)2

79
Q

what are some common salts (6)?

A

sulphates - made form sulphuric acids

chlorides - made from hydrochloric acid

nitrates - made from nitric acid

phosphates - made from phosphoric acid

ethanoates - made from ethanoic acid

citrates - made from citric acid

80
Q

what is the danger of copper compounds?

A

they are poisonous

81
Q

what is the danger of magnesium?

A

it is flammable and must be kept away from naked flames

82
Q

what is the danger of dilute sulphuric acid?

A

it is an irritant and must be washed off if it comes into contact with skin

83
Q

what is the danger of sodium hyroxide?

A

it is an irritant

84
Q

what is effervescence?

A

bubbles/bubbling

85
Q

what happens in any attempt to produce an insoluble salt from the reaction between a solid and a liquid? why?

A

it will fail

the salt produced will form a layer around the acid stopping any further reaction

86
Q

are barium compounds soluble in hyrdoxide compounds?

A

almost insoluble (slightly soluble)

87
Q

are calcium compounds soluble in sulphate compounds?

A

almost insoluble (slightly soluble)

88
Q

are calcium compounds soluble in hydroxide compounds?

A

almost insoluble (slightly soluble)

89
Q

all sodium, potassium and ammonium compouns are (soluble/insoluble)

A

all sodium, potassium and ammonium compouns are soluble

90
Q

all nitrates are (soluble/insoluble)

A

all nitrates are soluble

91
Q

all chlorides are (soluble/insoluble) except …

A

all chlorides are soluble except lead (II) chloride and silver chloride

92
Q

all sulphates are (soluble/insoluble) except …

A

all sulphates are soluble except lead (II) sulphate, barium sulphate and calcium sulphate which are slightly soluble

93
Q

all carbonates are (soluble/insoluble) except …

A

all carbonates are insoluble except sodium, potassium and ammonium carbonates

94
Q

all metal hydroxides are (soluble/insoluble) except …

A

all metal hydroxides are insoluble except sodium, potassium and ammonium hydroxides

95
Q

all ammonium salts are (soluble/insoluble)

A

all ammonium salts are soluble

96
Q

the alkalis are (soluble/insoluble)

A

the alkalis are soluble

97
Q

all other bases (not alkalis) are (soluble/insoluble)

A

all other bases (not alkalis) are insoluble

98
Q

all common acids are (soluble/insoluble)

A

all common acids are soluble

sulphuric acid

hydrochloric acid

nitric acid

phosphoric acid

ethanoic acid

tartaric acid

99
Q

making soluble salts involves reacting a … with an …

A

making soluble salts involves reacting a solid with an acid

100
Q

what ways can you make soluble salts by mixing an acid with something else?

A

acid + metal —> salt(aq) + hydrogen (only for moderately reactive metals from magnesium to iron on the reactivity series)

acid + alkali —> salt(aq) + water (+heat) - neutralisation

acid + metal oxide or hydroxide —> salt(aq) + water

acid + carbonate —> salt(aq) + water + carbon dioxide

101
Q

how do you make magnesium sulphate cyrstals?

A

add magnesium to dilute suphuric acid - make sure you add enough so that there is some left over when the reaction stops effervescing

filter off unused magnesium with filter paper and a funnel over an evaporating basin

concentrate the magnesium sulphate by boiling it in in the evaporating basin ontop of a gauze over a bunsen burner

test with a glass rod to see whether crystals form

leave the solution to form colourless magnesium sulphate crystals - any uncrystallised solution can be poured off the crystals

blot the crystals dry with a paper tissue

102
Q

why, when making soluble salts (except, sodium, potassium and ammonium), do we crystallise the solution slowly instead of boiling the water (which would be easier)?

A

evaportaing to dryness would not give you the crystals

instead, you would prodice an anhydrous salt

103
Q

what does anyhdrous mean?

A

without water

104
Q

what happens when many soluble salts (not sodium, potassium and ammonium) form their crystals?

A

water from the solution becomes chemically bound up in the salt - ‘water of crystallisation’

105
Q

what does it mean if a salt is hydrated?

A

the salt contains water of crystallisation

106
Q

in a reaction between an acid and a metal, what do you observe? why does this observation stop?

A

you observe effervescence but then it stops/is no longer observed because there is no acid left in the mixture or no more metal left to react

107
Q

what is crystallisation?

A

preparing a soluble salt by driving the water off

ions dissolve in solution, they are not bonded to the water molecules

108
Q

how do you prepare iron sulphate crystals?

A

add iron(II) oxide to hot dilute sulphuric acid - make sure you add an excess of iron oxide so there is some left over when the reaction stops effervescing

filter off unused iron oxide with filter paper and a funnel over an evaporating basin

concentrate the iron sulphate by boiling it in in the evaporating basin ontop of a gauze over a bunsen burner

test with a glass rod to see whether crystals form

leave the solution to form iron sulphate crystals - any uncrystallised solution can be poured off the crystals

blot the crystals dry with a paper tissue

109
Q

how do you know whether you need to heat the mixture?

A

carbonates and magnesium react with dilute acids in the cold

most other substances need to heated

110
Q

insoluble salts … well in water

A

insoluble salts do not dissolve well in water

111
Q

how can you prepare insoluble salts?

A

by a precipitation reaction

112
Q

what is a precipitate?

A

a fine solid that is formed by a chemical reaction involving liquids or gases

113
Q

when does a precipitation occur?

A

when you mix two solutions and as a result a precipitate forms

these two solutions contain soluble salts

114
Q

what is formed in a precipitation reaction?

A

a preciptate

a soluble salt

115
Q

where does the precipiate form in the beaker?

A

at the bottom

116
Q

explain what is happening when you react silver nitrate with sodium chloride?

A

silver nitrate solution contains silver ions and nitrate ions in solution

the positive and negative ions are attracted to each other but they are not strong enough to make them stick together

sodium chloride contains sodium ions and chloride ions and again, the attractions aren’t strong enough for them to stick together

when you mix the two solutions, the various ions meet each other

when the silver ions meet the chloride ions the attractions are so strong the ions clump together and form a solid

the sodium and nitrate ions remain in solution becuase they aren’t sufficiently attracted to each other

117
Q

what are spectator ions?

A

present in the reaction but do not change

118
Q

what is the equation for the precipitation reaction between copper sulphate and barium chloride?

A

copper sulphate + barium chloride —> copper chloride + barium sulphate

CuSO4 (aq) + BaCl2 (aq) —> CuCl2 (aq) + BaSO4 (s)

119
Q

what is the ionic and half equation for the precipitation reaction between copper sulphate and barium chloride?

A

ionic: Cu2+(aq) + SO42-<strong>(aq)</strong> + Ba2+(aq) + 2Cl-(aq) —> Cu2+(aq) + 2Cl-(aq) + BaSO4 (s)

half equation: SO42-(aq) + Ba2+(aq) —> BaSO4 (s)

120
Q

what is the equation for the precipitation reaction between sodium carbonate and magnesium sulphate?

A

sodium carbonate + magnesium sulphate —> sodium sulphate + magnesium carbonate

Na2CO3 (aq) + MgSO4 (aq) —> Na2SO4 (aq) + MgCO3 (s)

121
Q

what is the ionic and half equation for the precipitation reaction between sodium carbonate and magnesium sulphate?

A

ionic: 2Na+(aq) + CO32-(aq) + Mg2+(aq) + SO42-(aq) —> 2Na+(aq) + SO42-(aq) + MgCO3 (s)
half: CO32-(aq) + Mg2+(aq) —> MgCO3 (s)

122
Q

what is the equation for the precipitation reaction between calcium chloride and lead nitrate?

A

calcium chloride + lead nitrate —> calcium nitrate + lead chloride

CaCl2 + Pb(NO3)2 —>Ca(NO3)2 + PbCl2

123
Q

what is the ionic and half equation for the precipitation reaction between calcium chloride and lead nitrate?

A

ionic: Ca2+(aq) + Cl2-<strong>(aq)</strong> + Pb2+(aq) + (NO3)2- (aq) —> Ca2+(aq) + (NO3)2- (aq) + PbCl2 (s)
half: Cl2-(aq) + Pb2+(aq) —> PbCl2 (s)

124
Q

how do you carry out the indicator method/tiritation method? (Briefly)

A

add acid via burette to alkali and indicator using neutral (or until temperature stops rising)

measure volume of acid added; throw away solution

add the same volume of acid tosame amount of alkali without indicator

obtain dry salt from solution

125
Q

how do you carry out the obtaining dry salt from solution method? (Briefly)

A

concentrate solution until it becomes saturated which is don by driving off most of the water by heating it - solution is saturated when crystals form on a glass rod dipped in the solution

stop heating and allow solution to cool

cystals can be washed with distilled water

dry crystals with filter paper or place on warm gauze or in a warm place

126
Q

how do you carry out the neutralisation (acid + excess base/metal) method? (Briefly)

A

add excess base/metal to acid until no more dissolves (warm acid if necessary)

filter off excess base/metal

obtain salt from solution (using the obtaining dry salt from solution method)

127
Q

how do you carry out the precipitation method? (Briefly)

A

make solutions containing ions of salt to be made (need soluble salts)

add the solutions

filter of the precipitate

wash precipitate with distilled water

dry with filter paper or on warm gauze

128
Q

which method of making salts would you use if the salt isn’t soluble?

A

precipitation method

mix two solutions, one containing the correct positive ion and the other the correct negative ion

129
Q

which method of making salts would you use if the salt is soluble but is not sodium, potassium or ammonium salt?

A

react an acid with an excess of a solid metal (if suitably reactive), metal oxide, hydroxide or carbonate

130
Q

which method of making salts would you use if the salt is soluble and is not sodium, potassium or ammonium salt?

A

tiritation method

react an acid with a solution of sodium or potassium hydroxide or carbonate (or ammonia solution)

131
Q

how do you make copper sulphate?

A

Measure out 30cm3 of sulphuric acid

Place the acid into a 100cm3 beaker

Gently warm the acid using a BUnsen burner. Don’t not boil the acid or let it get hot

Add copper oxide one spatula at a time until it no longer reacts. You will be able to tell because there will be left over black copper oxide solid. Keep the acid warm - you may need to keep heating it for a few seconds, and then take the Bunsen away again

Filter and wash the mixture into a conical flask

Transfer the filtrate to an evaporating basin. Write your name on the basin using a permanent maker pen

Carefully put the evaporating basin on the tripod and guaze, making sure that it will not tip over esaily. Boil the copper sulphate solution until cyrstals start to form around the rim

When cool, place the dish in the place your teacher tells you

Next, lesson, filter and wash the crystals and leave them to dry on a peice of named filter paper

132
Q

write a word and balanced equation for making copper sulfate salt from copper oxide and sulphuric acid

A

copper oxide + sulphuric acid —-> copper sulphate + water

CuO (s) + H2SO4 (aq) —-> CuSO4 (aq) + H2O (l)

133
Q

Why is it important that there is no left over acid in the mixture when making copper sulfate salt?

A

as acid is corrosive/harmful

the copper sulphate would be impure

134
Q

How do you ensure there is no left over acid in the mixture when making copper sulfate salt?

A

you add an exess of copper oxide

135
Q

Why is it important that there is no left over base in the mixture when making copper sulfate salt?

A

oxide is harmful

the copper sulphate would be impure

136
Q

How do you ensure that there is no left over base in the mixture when making copper sulfate salt?

A

you filter off the excess copper oxide

137
Q

Why is the water not all evaporated when making copper sulfate salt?

A

water of crystallisation in product

138
Q

Explain why crystals form as the solution cooled when making copper sulfate salt?

A

the solvent can no longer hold all of the solute molecules, and they begin to leave the solution and form solid crystals

start with hot saturated solution, becomes less soluble as it cools

139
Q

How do you make sodium chloride?

A

Measure out 10cm3 of hydrochloric acid into a conical flask

Add 30cm3 of sodium hydroxide solution to the acid and swirl well

Test the pH of the mixture by dabbing a stirring rod from the mixture onto a piece of universal indicator paper

Add sodium hydroxide solution using a teating pipette until the mixture is neutral. If you add too much sodium hydroxide, then you will need to add some more hydrochloric acid.

When you have a neutral solution, transfer it to an evaporating basin, and boil it until the water has gone

Take care! - the sodium chloride solution may spit ot - when this starts to happen take the Bunsen burner away

140
Q

Write a word, balanced and ionic equation for making sodium chloride salt from sodium hydroxide and hydrochloric acid

A

sodium hydroxide + hydrochloric acid —> sodium chloride + water

NaOH (aq) + HCl (aq) —> NaCl (aq) + H2O (l)

ionic: Na+ + OH- (aq) + H+ + Cl- (aq) —> Na+ + Cl- (aq) + H2O (l)

141
Q

Why is it important that there is no left over acid in the mixture when making sodium chloride salt?

A

to make sure all the acid has been used

the acid is corrosive and irritant

142
Q

Why is it important that there is no left over alkali in the mixture when making sodium chloride salt?

A

it is corrosive

143
Q

Why do you do to make sure that there is no left over acid or alkali in the mixture when making sodium chloride salt?

A

test the mixture with litmus paper to make sure the solution is neutral (turning the indicator green)

144
Q

Why do you not add universal indicator mixture when making sodium chloride salt?

A

We want the salt to be white which indicates that it is pure

The universal indicator would have made the mixture colourful which indicates impurities. The universal indicator would be an impurity itself

145
Q

Why does it take a bigger volume of the sodium hydroxide solution than the hydrochloric acid for the acid to be neutralised when making sodium chloride salt?

A

the concentration of hydrochloric acid is greater than rhat of the sodium hydroxide so less is needed for it to be neutralised

146
Q

what does water of crystallisation mean?

A

the water molecules are chemically bonded to the salt

147
Q

are all acids ‘(aq)’?

A

yes

Chemisty (20 decks)

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