Acids Flashcards
1
Q
what is the range on the pH scale?
A
0 to about 14
2
Q
what does the pH scale tell you about a solution?
A
how acidic or alkaline it is
3
Q
what number on the pH scale is neutral?
A
7
4
Q
what number is most acidic on the pH scale?
A
0
5
Q
what number is most alkaline on the pH scale?
A
14
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
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
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
9
Q
what is a more accurate way than a universal indicator to measure the pH?
A
a pH meter
10
Q
what is a common indicator?
A
litmus
11
Q
what can be used as an indicator?
A
any substance that has more than one colour form depending on the pH
12
Q
what colour is litmus in acidic solution?
A
red
13
Q
what colour is litmus in alkaline solution?
A
blue
14
Q
what colour is litmus in neutral solution?
A
purple
15
Q
what colour is methyl orange in alkaline solutions?
A
yellow
16
Q
what colour is methyl orange in acidic solutions?
A
red
17
Q
what colour is phenolphthalien in alkaline solutions?
A
bright pink
18
Q
what colour is phenolphthalien in acidic solutions?
A
colourless
19
Q
what is an acid-base indicator?
A
chemicals that change to a different colour when the pH of a solution changes
20
Q
what colour is universal indicator in acidic solution?
A
strong red
21
Q
what colour is universal indicator in alkaline solution?
A
strong blue
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
23
Q
what does the pH show us?
A
the concentration of hydrogen ions in a solution compared to distilled water
24
Q
strong alkalines have … H+ ions
A
strong alkalines have very few H+ ions
25
strong acids have **...** H+ ions
strong acids have **many** H+ ions
26
what type of reaction is neutralisation?
exothermic
27
what is an acid?
a substance that, when dissolved in water, releases hydrogen H+ ions
28
what does dissociate mean?
to break apart
29
if an acid fully dissociates it is a **...** acid
if an acid fully dissociates it is a **strong** acid
30
if an acid partly dissociates it is a **...** acid
if an acid partly dissociates it is a **weak** acid
31
what is an alkali?
a base that can dissole in water
when dissolved in water, releases an OH- ion
32
what can alkalis do to acids?
neutralise them
33
what are bases?
substances that combine with hydrogen ions
react with acids to form a salt and water (and sometimes carbon dioxide as well)
usually metal oxides
34
what can bases do to acids?
neutralise them
35
do bases release a hydroxide ion when dissolved in water? why?
no
they do not dissolve in water
36
what do alkalis release when they fully dissociate?
hydroxide ions
37
what do alkalis release when they partly dissociate?
(less) hydroxide ions
38
are all alkalis bases or are all bases alkalis?
all alkalis are bases
not all bases are alkalis
39
what is formed when an acid reacts with an alkali? what is the balanced and ionic equation for this?
water
hydrogen + hydroxide ---\> water
H+ (aq) + OH- (aq) ---\> H2O (l)
40
metals below hydrogen in the reactivity series **...** with dilute acids
metals below hydrogen in the reactivity series **don't react** with dilute acids
41
metals above hydrogen in the reactivity series **...** with dilute acids
metals above hydrogen series **react** with dilute acids
42
the higher the metal in the reactivity series, the more **...** the reaction with an acid
the higher the metal in the reactivity series, the more **vigorous** the reaction with an acid
43
why would you never mix metals such as sodium or potassium with acids?
the reaction would be too vigorous
44
what is the summary equation for metals reacticing with acids?
acid (aq) + metal (s) ---\> salt (aq) + hyrogen (g)
45
what happens during a reaction between a metal and an acid?
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
46
what salts are formed from the parent acid sulphuric acid?
sulphates
47
what salts are formed from the parent acid hydrochloric acid?
chlorides
48
what salts are formed from the parent acid nitric acid?
nitrates
49
what happens when you react magnesium with dilute sulphuric acid?
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
50
what is the balanced equation for the reaction of magnesium with dilute sulphuric acid?
Mg(s) + H2SO4 (aq) ---\> MgSO4 (aq) + H2 (g)
51
what is the kind of reaction is the reaction of magnesium with dilute sulphuric acid? explain this breifly
a displacement reaction
the more reactive magnesium has displaced the less reactive hydrogen
52
what happens when you react magnesium with dilute hydrochloric acid?
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
53
what is the equation for the reaction of magnesium with dilute hydrochloric acid?
Mg(s) + 2HCl(aq) ---\> MgCl2 (aq) + H2 (g)
54
all acids in solution contain **...** ions
this means that magensium will react with any simple dilute acid in **...** way
all acids in solution contain **hyrogen** ions
this means that magensium will react with any simple dilute acid in **the same** way
55
the reaction of zinc with simple dilute acids is **...** than magnesium as zinc is **...** on the reactivity series
the reaction of zinc with simple dilute acids is **slower** than magnesium as zinc is **lower** on the reactivity series
56
how can the reaction of zinc with simple dilute acids be sped up?
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
57
how is hydrogen often made in the lab?
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)
58
how do you test for hydrogen?
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
59
what do most reactions between acids and metal oxides need? why?
heat to get the reaction started
60
what colour is copper (II) sulphate?
blue
61
what is the summary equation for acids and metal oxides?
acid(aq) + metal oxide(s) ---\> salt(aq) + water(l)
62
what happens during a reaction with an acid and a metal oxide?
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
what is the summary equation for the reacting acids and metal hydroxides (alkali)?
acid(aq) + metal hyrdoxide(aq) ---\> salt(aq) + water(l)
64
what happens during a reaction between an acid and a metal hydroxide?
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
do all metal hydroxides react with acids?
yes
66
solutions of soluble base are **(alkaline/acidic)** and have a pH of **(greater/lower)** than 7
solutions of soluble base are **alkaline** and have a pH of **greater** than 7
67
how can you tell excatly when enough acid has been added to an alkali to produce a neutral solution as everything involved is colourless?
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
around what pH does methyl orange change colour?
pH 4
69
carbonates react with cold dilute acids to produce **...**
carbonates react with cold dilute acids to produce **carbon dioxide**
70
what is the summary equation for acids and carbonates?
acid(aq) + metal carbonate(s) ---\> salt(aq) + water(l) +carbon dioxide(g)
71
what happens during a reaction between an acid and a metal carbonate?
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
what does carbon dioxide do to lime water?
turns it milky
73
an acid is a proton (hydrogen ion) **...**
an acid is a proton (hydrogen ion) **donor**
74
a base is a proton (hydrogen ion) **...**
a base is a proton (hydrogen ion) **acceptor**
75
what are salts?
ionic substances formed when acids react with bases
76
what are some common acids (6)?
sulphuric acid H2SO4
hydrochloric acid HCl
nitric acid HNO3
phosphoric acid H3PO4
ethanoic acid C2H4O2
tartaric acid C4H6O6
77
what are some common bases (3)?
metal oxides
metal hydroxides
metal carbonates
78
what are some common alkalis (1) and water soluble metal hydroxides (3)?
**common alkalis:**
ammonia NH3
**common water soluble metal hydroxides:**
sodium hydroxide NaOH
potassium hydroxide KOH
calcium hydroxide Ca(OH)2
79
what are some common salts (6)?
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
what is the danger of copper compounds?
they are poisonous
81
what is the danger of magnesium?
it is flammable and must be kept away from naked flames
82
what is the danger of dilute sulphuric acid?
it is an irritant and must be washed off if it comes into contact with skin
83
what is the danger of sodium hyroxide?
it is an irritant
84
what is effervescence?
bubbles/bubbling
85
what happens in any attempt to produce an insoluble salt from the reaction between a solid and a liquid? why?
it will fail
the salt produced will form a layer around the acid stopping any further reaction
86
are barium compounds soluble in hyrdoxide compounds?
almost insoluble (slightly soluble)
87
are calcium compounds soluble in sulphate compounds?
almost insoluble (slightly soluble)
88
are calcium compounds soluble in hydroxide compounds?
almost insoluble (slightly soluble)
89
all sodium, potassium and ammonium compouns are **(soluble/insoluble)**
all sodium, potassium and ammonium compouns are **soluble**
90
all nitrates are **(soluble/insoluble)**
all nitrates are **soluble**
91
all chlorides are **(soluble/insoluble)** except **...**
all chlorides are **soluble** except **lead (II) chloride** and **silver chloride**
92
all sulphates are **(soluble/insoluble)** except **...**
all sulphates are **soluble** except **lead (II) sulphate**, **barium sulphate** and **calcium sulphate** which are slightly soluble
93
all carbonates are **(soluble/insoluble)** except **...**
all carbonates are **insoluble** except **sodium**, **potassium** and **ammonium carbonates**
94
all metal hydroxides are **(soluble/insoluble)** except **...**
all metal hydroxides are **insoluble** except **sodium**, **potassium** and **ammonium hydroxides**
95
all ammonium salts are **(soluble/insoluble)**
all ammonium salts are **soluble**
96
the alkalis are **(soluble/insoluble)**
the alkalis are **soluble**
97
all other bases (not alkalis) are **(soluble/insoluble)**
all other bases (not alkalis) are **insoluble**
98
all common acids are **(soluble/insoluble)**
all common acids are **soluble**
sulphuric acid
hydrochloric acid
nitric acid
phosphoric acid
ethanoic acid
tartaric acid
99
making soluble salts involves reacting a **...** with an **...**
making soluble salts involves reacting a **solid** with an **acid**
100
what ways can you make soluble salts by mixing an acid with something else?
**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
how do you make magnesium sulphate cyrstals?
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
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)?
evaportaing to dryness would not give you the crystals
instead, you would prodice an anhydrous salt
103
what does anyhdrous mean?
without water
104
what happens when many soluble salts (not sodium, potassium and ammonium) form their crystals?
water from the solution becomes chemically bound up in the salt - 'water of crystallisation'
105
what does it mean if a salt is hydrated?
the salt contains water of crystallisation
106
in a reaction between an acid and a metal, what do you observe? why does this observation stop?
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
what is crystallisation?
preparing a soluble salt by driving the water off
ions dissolve in solution, they are not bonded to the water molecules
108
how do you prepare iron sulphate crystals?
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
how do you know whether you need to heat the mixture?
carbonates and magnesium react with dilute acids in the cold
most other substances need to heated
110
insoluble salts **...** well in water
insoluble salts **do not dissolve** well in water
111
how can you prepare insoluble salts?
by a precipitation reaction
112
what is a precipitate?
a fine solid that is formed by a chemical reaction involving liquids or gases
113
when does a precipitation occur?
when you mix two solutions and as a result a precipitate forms
these two solutions contain soluble salts
114
what is formed in a precipitation reaction?
a preciptate
a soluble salt
115
where does the precipiate form in the beaker?
at the bottom
116
explain what is happening when you react silver nitrate with sodium chloride?
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
what are spectator ions?
present in the reaction but do not change
118
what is the equation for the precipitation reaction between copper sulphate and barium chloride?
copper sulphate + barium chloride ---\> copper chloride + barium sulphate
CuSO4 (aq) + BaCl2 (aq) ---\> CuCl2 (aq) + BaSO4 (s)
119
what is the ionic and half equation for the precipitation reaction between copper sulphate and barium chloride?
ionic: Cu2+(aq) + **SO42-**(aq) + **Ba2+(aq) **+ 2Cl-(aq) ---\> Cu2+(aq) + 2Cl-(aq) + **BaSO4 (s)**
half equation: SO42-(aq) + Ba2+(aq) ---\> BaSO4 (s)
120
what is the equation for the precipitation reaction between sodium carbonate and magnesium sulphate?
sodium carbonate + magnesium sulphate ---\> sodium sulphate + magnesium carbonate
Na2CO3 (aq) + MgSO4 (aq) ---\> Na2SO4 (aq) + MgCO3 (s)
121
what is the ionic and half equation for the precipitation reaction between sodium carbonate and magnesium sulphate?
ionic: 2Na+(aq) + **CO32-(aq)** + **Mg2+(aq)** + SO42-(aq) ---\> 2Na+(aq) + SO42-(aq) + **MgCO3 (s)**
half: CO32-(aq) + Mg2+(aq) ---\> MgCO3 (s)
122
what is the equation for the precipitation reaction between calcium chloride and lead nitrate?
calcium chloride + lead nitrate ---\> calcium nitrate + lead chloride
CaCl2 + Pb(NO3)2 ---\>Ca(NO3)2 + PbCl2
123
what is the ionic and half equation for the precipitation reaction between calcium chloride and lead nitrate?
ionic: Ca2+(aq) + **Cl2-**(aq) + **Pb2+(aq)** + (NO3)2- (aq) ---\> Ca2+(aq) + (NO3)2- (aq) + **PbCl2 (s)**
half: Cl2-(aq) + Pb2+(aq) ---\> PbCl2 (s)
124
how do you carry out the indicator method/tiritation method? (Briefly)
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
how do you carry out the obtaining dry salt from solution method? (Briefly)
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
how do you carry out the neutralisation (acid + excess base/metal) method? (Briefly)
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
how do you carry out the precipitation method? (Briefly)
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
which method of making salts would you use if the salt isn't soluble?
**precipitation method**
mix two solutions, one containing the correct positive ion and the other the correct negative ion
129
which method of making salts would you use if the salt is soluble but is not sodium, potassium or ammonium salt?
react an acid with an excess of a solid metal (if suitably reactive), metal oxide, hydroxide or carbonate
130
which method of making salts would you use if the salt is soluble and is not sodium, potassium or ammonium salt?
**tiritation method**
react an acid with a solution of sodium or potassium hydroxide or carbonate (or ammonia solution)
131
how do you make copper sulphate?
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
write a word and balanced equation for making copper sulfate salt from copper oxide and sulphuric acid
copper oxide + sulphuric acid ----\> copper sulphate + water
CuO (s) + H2SO4 (aq) ----\> CuSO4 (aq) + H2O (l)
133
Why is it important that there is no left over acid in the mixture when making copper sulfate salt?
as acid is corrosive/harmful
the copper sulphate would be impure
134
How do you ensure there is no left over acid in the mixture when making copper sulfate salt?
you add an exess of copper oxide
135
Why is it important that there is no left over base in the mixture when making copper sulfate salt?
oxide is harmful
the copper sulphate would be impure
136
How do you ensure that there is no left over base in the mixture when making copper sulfate salt?
you filter off the excess copper oxide
137
Why is the water not all evaporated when making copper sulfate salt?
water of crystallisation in product
138
Explain why crystals form as the solution cooled when making copper sulfate salt?
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
How do you make sodium chloride?
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
Write a word, balanced and ionic equation for making sodium chloride salt from sodium hydroxide and hydrochloric acid
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
Why is it important that there is no left over acid in the mixture when making sodium chloride salt?
to make sure all the acid has been used
the acid is corrosive and irritant
142
Why is it important that there is no left over alkali in the mixture when making sodium chloride salt?
it is corrosive
143
Why do you do to make sure that there is no left over acid or alkali in the mixture when making sodium chloride salt?
test the mixture with litmus paper to make sure the solution is neutral (turning the indicator green)
144
Why do you not add universal indicator mixture when making sodium chloride salt?
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
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?
the concentration of hydrochloric acid is greater than rhat of the sodium hydroxide so less is needed for it to be neutralised
146
what does water of crystallisation mean?
the water molecules are chemically bonded to the salt
147
are all acids '(aq)'?
yes
