7. Acids, bases and salts Flashcards
(248 cards)
1
Q
What pH value do acids have?
A
Acids have pH values of below 7
2
Q
What property do acids have which makes them dangerous?
A
They’re corrosive
3
Q
What colour does blue litmus paper turn in acidic conditions?
A
Blue litmus paper turns red
4
Q
What colour does methyl orange indicator turn in acidic conditions?
A
methyl orange indicator turns red
5
Q
What can acids do to bases?
A
Acids are substances that can neutralise a base, forming a salt and water
6
Q
When acids react, what will they form? (in terms of ions)
A
When acids react, they will lose electrons to form positively charged hydrogen ions (H+)
7
Q
What makes a solution acidic?
A
The presence of H+ ions is what makes a solution acidic
8
Q
What metals react with dilute acids?
A
Only metals above hydrogen in the reactivity series will react with dilute acids.
9
Q
What is formed when metals react with acid?
A
When acids react with metals they form a salt and hydrogen gas:
Acid + Metal → Salt + Hydrogen
10
Q
What type of oxides are metal oxides and metal hydroxides?
A
Metal oxides and metal hydroxides can act as bases
11
Q
What happens when metal oxides/hydroxides react with acid?
A
When they react with acid, a neutralisation reaction occurs
12
Q
What is produced by a neutralisation reaction?
A
In all acid-base neutralisation reactions, salt and water are produced
Acid + Base → Salt + Water
13
Q
What happens when an acid reacts with a metal carbonate? products?
A
Acids will react with metal carbonates to form the corresponding metal salt, carbon dioxide and water:
Acid + Metal Carbonate → Salt + Carbon Dioxide + Water
14
Q
What pH do bases have?
A
Bases have pH values of above 7
15
Q
What is an alkali?
A
A base which is water-soluble is referred to as an alkali
16
Q
What colour does red litmus paper turn in alkaline conditions?
A
In basic (alkaline) conditions red litmus paper turns blue
17
Q
What colour does methyl orange indicator turn in alkaline conditions?
A
methyl orange indicator turns yellow
18
Q
In what ways can bases react with acids?
A
Bases are substances which can neutralise an acid, forming a salt and water
19
Q
In what forms do bases usually appear?
A
Bases are usually oxides or hydroxides of metals
20
Q
What happens to alkalis when they react? (in terms of ions)
A
When alkalis react, they gain electrons to form negative hydroxide ions (OH–)
21
Q
What makes a solution alkaline
A
The presence of the OH– ions is what makes the aqueous solution an alkali
22
Q
What happens to ammonium salts when warmed with an alkali?
A
Ammonium salts undergo decomposition when warmed with an alkali
23
Q
What makes ammonia dangerous? How can this problem be fixed?
A
Even though ammonia is itself a weak base, it is very volatile and can easily be displaced from the salt by another alkali
24
Q
What is produced in the reaction between alkalis and ammonium salts?
Give an example equation between ammonium chloride and sodium hydroxide
A
A salt, water and ammonia are produced
Example:
NH4Cl + NaOH →NaCl + H2O + NH3
25
What is the reaction between ammonium chloride and sodium hydroxide used for?
This reaction is used as a chemical test to confirm the presence of the ammonium ion (NH4+)
26
How does the test for ammonia work?
Alkali is added to the substance with gentle warming followed by the test for ammonia gas using damp red litmus paper
The litmus paper will turn from red to blue if ammonia is present
27
What is the pH scale?
The pH scale is a numerical scale which is used to show how acidic or alkaline a solution is
28
From what scale does the pH scale range?
0-14
29
What does it mean if the pH value of an acid is very low?
The lower the pH then the more acidic the solution is
30
What does it mean if the pH value of an alkali is very high?
The higher the pH then the more alkaline the solution is
31
What does it mean if a substance has a pH of 7?
A solution of pH 7 is describe as being neutral e.g. water
32
What type of indicator can be used to measure pH?
Universal indicator is a mixture of different indicators which is used to measure the pH
33
How is universal indicator used?
A drop is added to the solution and the colour is matched with a colour chart which indicates the pH which matches specific colours
34
Why is soil pH analysed?
Soil pH is analysed to indicate the acidity or alkalinity of soil
35
What PH’s do most plants favour?
Most plants favour a pH value of between 5 and 8
36
What happens if the soil pH is not ideal for the plant?
Changes in soil which cause a pH to be outside this range adversely affect plant processes resulting in reduced growth and crop yield
37
How may soils become acidic?
Soils may become acid from acid rain, overuse of fertilisers which contain ammonium salts or by the excessive breakdown of organic matter by bacteria
38
How can soil be neutralised?
Crushed or powdered limestone (calcium carbonate) or lime (calcium oxide) or slaked lime (calcium hydroxide) is added to neutralise the excess acidity in the soil
39
Why must the process in which soil is neutralised be monitored?
The addition process must be carefully monitored though, as if added in excess, further damage could be done if the pH goes too high
40
What are acids? (in terms of protons) Why?
Acids are proton donors as they ionize in solution producing protons, H+ ions
41
What are alkalis? (in terms of protons) Why?
Bases (alkalis) are proton acceptors as they ionize in solution producing OH– ions which can accept protons
42
What determines whether an acid or base is strong or weak?
Acids and alkalis can be either strong or weak, depending on how many ions they produce when dissolved in water
43
What determines a strong acid or alkali?
Strong acids and bases ionize completely in water, producing solutions of very low pH for an acid or very high pH for a base
44
What are examples of strong acids and bases?
Strong acids include HCl and H2SO4 and strong bases include the Group I hydroxides
45
What determines a weak acid or base?
Weak acids and bases partially ionize in water and produce pH values which are closer to the middle of the pH scale
46
What are examples of weak acids?
Weak acids include organic acids such as ethanoic acid, CH3COOH
47
What are examples of weak bases?
weak bases include aqueous ammonia
48
What is usually set-up for both weak acids and bases once they’re added to water?
For both weak acids and bases, there is usually an equilibrium set-up between the molecules and their ions once they have been added to water
49
Give an example for the ions forming aqueous ammonia
NH3 + H2O ⇌ NH4+ + OH-
50
In the example for aqueous ammonia and its ions, to which direction does the equilibrium lie and why?
In both cases the equilibrium lies to the left, indicating a high concentration of intact acid / base molecules, with a low concentration of ions in solution
51
What determines if a solution of an acid or base is concentrated?
A concentrated solution of either an acid or a base is one that contains a high number of acid or base molecules per dm3 of solution
52
Is a concentrated acid strong?
NO
It does not necessarily mean that the acid or base is strong though, as it may be made from a weak acid or base which does not dissociate completely
53
Do acidic and basic oxides have the same properties?
NO
Acidic and basic oxides have different properties and values of pH
54
What determines the pH of an oxide?
The difference in their pH stems from whether they are bonded to a metal or a nonmetal element
55
What does the metallic character influence? (oxides)
The metallic character of the element influences the acidic or alkaline behaviour of the molecule
56
When are acidic oxides formed?
Acidic oxides are formed when a nonmetal element combines with oxygen
57
What happens when an acidic oxide is dissolved in water?
When dissolved in water they produce an acidic solution with a low pH
58
What happens when an acidic oxide reacts with a base?
They react with bases to form a salt and water
59
What are common examples of acidic oxides?
Common examples include SO2 and SiO2
60
When are basic oxides formed?
Basic oxides are formed when a metal element combines with oxygen
61
What happens when a basic oxide is dissolved in water?
When dissolved in water they produce a basic solution with a high pH
62
What happens when a basic oxide reacts with an acid?
They react with acids to form a salt and water
63
What are common examples of basic oxides?
Common examples include NaOH, KOH and Ca(OH)2
64
What are neutral oxides?
Some oxides do not react with either acids or bases and thus are said to be neutral
65
What are examples of neutral oxides?
Examples include N2O, NO and CO
66
What are amphoteric oxides?
Amphoteric oxides are a curious group of oxides that can behave as both acidic and basic, depending on whether the other reactant is an acid or a base
67
What is formed when an amphoteric oxide reacts with an acid or a base?
In both cases a salt and water is formed
68
What are examples of amphoteric oxides?
Two most common amphoteric oxides are zinc oxide and aluminum oxide
69
Do the hydroxides of zinc and aluminium also react amphoterically?
YES
70
What is a salt?
A salt is a compound that is formed when the hydrogen atom in an acid is replaced by a metal
71
How can salts be used?
These uses include fertilisers, batteries, cleaning products, healthcare products and fungicides
72
How many parts does the name of a salt have?
The name of a salt has two parts
73
Where does the first part of a salt name come from?
The first part comes from the metal, metal oxide or metal carbonate used in the reaction
74
Where does the second part of the salt name come from?
The second part comes from the acid
75
how can the name of a salt be determined?
The name of the salt can be determined by looking at the reactants
76
What are two key things to consider when preparing salts?
Is the salt being formed soluble or insoluble in water?
- Is there water of crystallisation present in the salt crystals?
77
Are sodium, potassium and ammonium salts soluble?
Yes, all of them are
78
Are nitrates soluble?
Yes, all of them are
79
Are ethanoates soluble?
Yes, all of them are
80
Are chlorides soluble?
Most of them,
Exceptions include:
Silver and Lead(II)
81
Are sulfates soluble?
Most of them,
Exceptions include:
Barium, Calcium and Lead (II)
82
Are carbonates soluble?
Most of them are INSOLUBLE,
Exceptions include:
Sodium, potassium and ammonium
83
Are hydroxides soluble?
Most of them are INSOLUBLE,
Exceptions include:
Sodium, potassium and calcium (calcium hydroxide is slightly soluble)
84
8.2.1 look at methods of salt preparation
:)
85
Alkali ions
OH-
86
Acid ions
H+
87
pH of pure water
pH 7
88
Salt
A compound formed when some or all of the hydrogen in an acid is replaced by a metal.
89
Acid + Metal ->
Salt + Hydrogen
90
Acid + Base ->
Salt + Water
Neutralisation reaction
91
Acid + Base ->
Salt + Water
Neutralisation reaction
92
Acid + Alkali ->
Salt + Water
Neutralisation reaction
93
Precipitate
An insoluble solid formed by a reaction taking place in a solution.
94
How are precipitation reactions used?
To remove pollutants from the waste water produced by factories.
To remove metal ions from industrial waste water.
Remove unwanted ions from drinking water.
95
Acid + Metal Carbonate ->
Salt + Water + CO2
96
Test for CO2
Limewater solution.
97
How to carry out a Titration
Measure a known volume of alkali into a flask using a volumetric pipette. Measure from the bottom of the Meniscus.
Add a few drops of indicator (thymolphthalein- Blue in alkali, colourless in acid)
Pour acid into a Burette. Drop into alkali until alkali changes colour.
Measure how much acid it took, an repeat until you get two identical results.
98
Where does the alkali go in a Titration?
The flask.
99
sums to remember
conc = mol/ vol and mol = mass/ Mr
100
All salts of group I
soluble
101
All ammonium salts
soluble
102
All nitrates
soluble
103
All nitrates
soluble
104
Most halides
soluble
105
Silver and lead halides
insoluble
106
Group I hydroxides/carbonates
soluble
107
Most hydroxides/carbonates
insoluble
108
Group I & II oxides in water
soluble
109
Most metal oxides
insoluble
110
What is the role of the pH scale?
pH scale is used to show the acidity or alkalinity of a solution
111
What is an acid? (2)
Substance that form hydrogen ions when dissolved in water
proton donor
112
metal + acid →
salt + hydrogen
113
alkali + acid →
salt + water
114
What type of reaction is an metal + acid reaction?
redox reaction
115
metal hydroxide + acid →
salt + water
116
metal carbonate + acid →
salt + water + carbon dioxide
117
What is a base that is soluble in water?
Alkali
118
acid + base →
salt + water
119
Ammonia salts are much more _ than metal salts
volatile
120
alkali + ammonium salt →
metal salt + ammonia + water
121
What happens when acids react with a metal oxides?
When acids react with metals they form a salt and hydrogen gas:
Acid + Metal oxides → Salt + Hydrogen.
122
What happens when acids react with bases?
In all acid-base neutralisation reactions, salt and water are produced:
Acid + Base → Salt + Water.
123
What happens when acids react with metal carbonates?
Acids will react with metal carbonates to form the corresponding metal salt, carbon dioxide and water:
Acid + Metal Carbonate → Salt + Carbon Dioxide + Water.
124
Describe the effect on litmus, thymolphthalein and methyl orange in acidic conditions.
In acidic conditions, blue litmus paper turns red, thymolphthalein turns colourless and methyl orange indicator turns red.
125
What are the three important properties of acids?
Acids have pH values of below 7, have a sour taste (when edible) and are corrosive.
126
What are acids?
Acids are substances that will lose electrons to form positively charged hydrogen ions (H+ also called protons) when dissolved in water.
127
What is an indicator?
A substance which changes color when added to acidic or alkaline solutions.
128
What is a base?
Bases are substances which can neutralise an acid, forming a salt and water.
129
What is an alkali?
An alkali is a soluble base.
130
Describe the effect on litmus, thymolphthalein and methyl orange in basic (alkaline) conditions?
In basic (alkaline) conditions red litmus paper turns blue, thymolphthalein turns blue and methyl orange indicator turns yellow.
131
What four substances can bases be?
Bases can be metal oxides, metal hydroxides, ammonia or carbonates of metals.
132
What is a neutralisation reaction?
When a base reacts with an acid to form a salt we call the reaction a neutralization reaction.
133
What do acids and alkalis produce in aqueous solutions?
Acids produce H+ ions in aqueous solutions.
Alkalis produce OH- ions in aqueous solutions.
134
What does the pH scale measure and describe neutrality, acidity, and alkalinity through whole numbers?
The pH scale (0 to 14) measures the acidity or alkalinity of a solution, and can be measured using a universal indicator:
The lower the pH then the more acidic the solution is.
A solution with a pH of 7, such as water, is described as being neutral.
The higher the pH then the more basic the solution is.
135
Soil may become acidic after a number of years. This can be due to:
Give three examples.
Acid rain.
Bacteria and fungi rotting the vegetation so that it releases acids.
Use of fertilizers containing ammonium salts.
136
What is used to neutralize excess acidity in soil?
Crushed limestone (calcium carbonate) or lime (calcium oxide) are added to neutralise excess acidity in the soil.
137
Describe the importance of controlling acidity in soil?
If the pH of the soil is too acidic or too basic this would mean that crops would be unable to grow well.
138
What are acids in terms of proton transfer?
Acids are proton donors as they ionise in solution producing protons, which are H+ ions.
NOTE - These H+ ions make the aqueous solution acidic.
139
What are bases in terms of proton transfer?
Bases (alkalis) are proton acceptors as they ionise in solution producing OH- ions which can accept protons.
NOTE - These OH- ions make the aqueous solution alkaline.
140
Describe the meaning of strong acids.
Strong acids ionise completely in water, producing solutions of very low pH for an acid.
141
Describe the meaning of strong bases.
Strong bases ionise completely in water producing solutions of very high pH for a base.
142
Describe the meaning of weak acids.
Weak acids partially ionise in water and produce pH values which are closer to the middle of the pH scale.
143
Describe the meaning of weak bases.
Weak bases partially ionise in water and produce pH values which are closer to the middle of the pH scale.
144
We can tell if an acid is strong or weak by measuring its electrical conductivity, pH and rate of reaction with metals or metal carbonates:
A strong acid conducts much better than a weak acid of the same concentration.
A strong acid has a lower pH than weak acid of the same concentration.
A strong acid reacts faster than a weak acid.
145
We can tell is an acid is strong or weak by measuring its electrical conductivity, pH and rate of reaction with metals or metal carbonates.
What are the reasons for these differences?
This is because there is a greater concentration of hydrogen ions in the strong acid compared with the weak acid.
146
Compared with strong bases, weak bases have:
A lower electrical conductivity.
A less alkaline (lower) pH.
A slower rate of reaction.
147
What is a universal indicator?
A universal indicator is a mixture of different indicators which is used to measure the pH.
148
What are oxides?
Oxides are compounds of metal or non-metals.
149
What are the four types of oxides?
Acidic oxides.
Neutral oxides.
Amphoteric oxides.
Basic oxides.
150
When are basic oxides formed?
Basic oxides are formed when a metal element combines with oxygen
151
What happens when a metal reacts with oxygen (basic oxide reaction)?
Metal + oxygen → salt.
152
What happens when basic oxides are dissolved in water?
When dissolved in water they produce a basic solution with a high pH.
153
Give three examples of basic oxides.
CuO - Copper oxide.
CaO - Calcium oxide.
BaO - Barium oxide.
MgO - Magnesium oxide.
Fe₂O₃ - Iron (III) oxide.
154
When are acidic oxides formed?
Acidic oxides are formed when a non-metal element combines with oxygen.
155
What happens when basic oxides react with acid?
What happens when acidic oxides react with bases?
Basic oxides + acid → salt + water.
Acidic oxides + base → salt + water.
156
What happens when acidic oxides are dissolved in water?
When dissolved in water they produce an acidic solution with a low pH.
157
Give three examples of acidic oxides.
SO₂ - Sulfur dioxide.
CO₂ - Carbon dioxide.
P₂O5 - Phosphorus pentoxide.
SO₃ - Sulfur trioxide.
NO₂ - Nitrogen dioxide.
158
What are neutral oxides?
Neutral oxides do not react with acids or bases.
159
Give three examples of neutral oxides.
N₂0 - Nitrous Oxide.
NO - Nitrogen monoxide.
CO - Carbon monoxide.
160
What are amphoteric oxides?
Amphoteric oxides are a curious group of oxides that can behave as both acidic and basic, depending on whether the other reactant is an acid or a base.
NOTE - In both cases, a salt and water is formed.
161
Give two examples of amphoteric oxides.
ZnO - Zinc oxide.
Al2O3 - Aluminium oxide.
162
What are the four common laboratory acids?
Hydrochloric acid - HCl.
Sulfuric acid - H₂SO₄.
Nitric acid - HNO₃.
Phosphoric acid - H₃PO₄
163
What makes an acidic solution acidic?
All acids form hydrogen ions (H+) when dissolved in water, it is the hydrogen ions that make a solution acidic.
164
What are three common laboratory bases?
Sodium hydroxide - NaOH.
Calcium hydroxide - Ca(OH)₂.
Ammonia - NH₃.
165
What do alkalis form when dissolved in water?
Alkalis form hydroxide ions (OH-) when they dissolve in water.
166
What is a salt?
A salt is a compound that is formed when the hydrogen atom in an acid is replaced by a metal/an ammonium group (NH₄).
167
What happens when an acid reacts with a metal hydroxide?
Metal hydroxide + acids → salt + water.
168
When is a hydrogen ion formed?
A
A hydrogen ion is formed by the removal of the single electron from a hydrogen atom.
169
What are the four ways of making salts?
Reacting a metal with an acid.
Reacting an insoluble base with an acid.
Neutralising an alkali with an acid by the titration method.
By precipitation.
170
How do you make a salt from an insoluble base (3)?
add excess base to the acid.
filter to remove any unreacted base that’s been added.
heat the solution to evaporate the water, allowing crystals of the salt to form.
171
How do you make a salt from an soluble base (titration is the making of a soluble salt from a soluble base and acid) (7)?
Measure the alkali into the titration flask using a volumetric pipette.
Add a few drops of indicator solution to the alkali in the flask.
Fill a clean burette with acid.
Record the burette reading.
Open the burette tap and let the acid flow into the flask.
Keep adding acid slowly until the indicator changes color.
Record the reading on the burette.
172
How do we make a salt from metals (6)?
Add the metal to the acid in the flask so that the metal is in excess.
Warm the flask gently to complete the reaction.
Filter off the excess metal.
Put the filtrate into an evaporating basin and evaporate the water until the crystalisation point is reached.
Filter off the crystals and wash them with distilled water.
Dry the crystals between sheets of filter paper.
173
What is a titration?
A titration is used to make a soluble salt from an acid.
To conduct a titration both acid and alkali must be soluble.
174
What are the salts made by the titration method included in?
Salts made by the titration method include salts of Group 1 elements and ammonium salts.
175
What is a precipitate?
The solid obtained when solutions of two soluble compounds are mixed is called a precipitate.
176
What are the 7 soluble compounds?
All salts of Group 1 elements.
All nitrates.
All ammonium salts.
Most chlorides, bromides and iodides (halides).
Most sulfates.
Group I hydroxide and carbonates are soluble.
Group I and II oxides react with water.
177
What are the 4 insoluble compounds (precipitation)?
Chlorides, bromides and iodides of silver and lead.
Sulfates of calcium, barium and lead.
Most hydroxide and carbonates.
Most metal oxides.
178
How do we make an insoluble salt (precipitation)?
making insoluble salts:
- mix the two solutions that will form the salt.
- filter to remove the solid insoluble salt.
- wash salt with distilled water.
- leave salt to dry on filter paper.
179
What are spectator ions?
The ions that do not take part in the reaction are called spectator ions.
180
Decribe the test for ammonia.
Turns damp red litmus paper blue.
181
Describe the test for carbon dioxide.
Bubble the gas through the limewater and it will turn milky (cloudy)
182
Describe the test for chlorine gas?
When damp litmus paper is put into chlorine gas the litmus paper is bleached and turns white.
183
Describe the test for hydrogen gas.
Use a burning splint held at the open end of a test tube of the gas.
▪ Creates a ‘squeaky pop’ sound.
184
Describe the test for oxygen gas.
Uses a glowing splint inserted into a test tube of the gas.
▪ Splint relights in oxygen.
185
Describe the test for sulfur dioxide.
Use aqueous potassium manganate(VII) and there will be a colour change from purple to colourless.
186
What is the formula for percentage composition?
% composition = Ar (X) ÷ Mr (XY) x 100.
187
What is a saturated solution?
A solution in which no more solute will dissolve.
188
What is an acid?
Proton donor
HCl dissociates (breaks apart) in water to give H+ ions
189
What is a base?
A proton acceptor
190
What is an alkali?
An alkali is a soluble base which dissociates in water making an OH- ion
Example NaOH is a soluble base, it dissociates into Na+ and OH- in water
191
Name three common acids
Hydrochloric acid
HCl
Sulphuric acid
H2SO4
Nitric acid
HNO3
192
Name three common alkali.
sodium hydroxide
NaOH
Potassium hydroxide
KOH
Ammonium hydroxide
NH4OH
193
What is the chemical formula for hydrochloric acid?
HCl
194
What is the chemical formula for sulphuric acid?
H2SO4
195
What is the chemical formula for nitric acid?
HNO3
196
What is the chemical formula for carbonic acid?
H2CO3
197
Complete the general equation
Acid + Alkali –>
Acid + Alkali –> Salt + Water
198
Explain how an alkali can neutralise an acid.
You need to add an indicator such as thymolphthalein to a sample of the alkali. It will turn blue.
Add small drops of the acid using a pipette until one drop turn the solution from pink to colourless.
You now have equal numbers of H+ ions and OH- ions making H2O or water
199
Name three bases
Copper oxide
CuO
Aluminium oxide
Al2O3
Copper hydroxide
Cu(OH)2
200
What colour is methyl orange in acid and alkali?
https://www.google.co.uk/search?sa=G&hl=en-GB&q=methyl+orange+in+alkali&tbm=isch&tbs=simg:CAQSlgEJWz3N6x9eNpoaigELEKjU2AQaBAgICAoMCxCwjKcIGmEKXwgDEifvBq0ChgGHAawCqgKdAZIB5wMKyTSOJ58o5zS1KO02zSGrJ8g0nSAaMI2JhdVCfe4ww-KXkTV2fPsc3WJmrVKc5ng0PtdEvmoXgq–OHHrQIs3KbCDynaetyAEDAsQjq7-CBoKCggIARIEtLIVuQw&ved=0ahUKEwiy_Z7ohpvUAhXKLcAKHWm4B7oQwg4IIygA
acid - red
alkali- yellow
201
Finish the general equation
Acid + metal carbonate –>
Spot the carbonate!
Think neutralisation + carbon dioxide
Acid + metal carbonate –> Salt + water + carbon dioxide
202
Finish the general equation
Acid + metal carbonate –>
Spot the carbonate!
Think neutralisation + carbon dioxide
Acid + metal carbonate –> Salt + water + carbon dioxide
203
What colour is thymolphthalein in acid and alkali?
Acid - colourless
Alkali- blue
204
What colour is litmus in acid and alkali?
Acid- red
Alkali- blue
205
What colour is univeral indicator in strong acid, weak acid, neutral, weak alkali and strong alkali?
strong acid- red
weak acid- yellow
neutral- green
weak alkali- blue
strong alkali- purple
206
Name a strong acid and strong alkali
strong acid- HCl - stomach acid pH 2
strong alkali - NaOH - pH 14
207
Name a weak acid and alkali
weak acid - carbonic acid
weak alkali - ammonia
208
Name a neutral substance
water- universal indicator turns green
209
Finish the reaction
HCl + NaOH –>
This is an acid + alkali - think neutralisation!
Salt + water!
HCl + NaOH –> NaCl + H2O
210
Finish the reaction
H2SO4 + KOH –>
This is an acid + alkali - think neutralisation
salt + water
remember a salt is metal/non-metal or cation/anion
H2SO4 (aq) + 2KOH(aq) –> K2SO4 (aq) + 2H2O (l)
don’t forget to balance it!
211
Finish the general reaction
Acid + base –>
acid + base –> salt + water
212
How do you spot an acid from its chemical formulae?
All acids have a hydrogen atom at the front of the chemical formula
HCl
H2SO4
H2CO3
HNO3
213
How do you spot a base from its chemical formulae?
The chemical formula would end with an oxide, hydroxide or carbonate
CuO
Mg(OH)2
Na2CO3
214
What will the products be in this reaction?
HNO3 + CuO –>
This is an acid + base- think neutralisation
salt + water
2HNO3(aq) + CuO(s) –> Cu(NO3)2 (aq) + H2O(l)
Think of your solubility rules to help figure out the state symbols
All oxides are insoluble except for Na, K or NH4+ - therefore CuO (s)
All nitrate salts are soluble- therefore Cu(NO3)2 (aq)
215
What will the products be?
HNO3 + CaCO3 –>
Spot the carbonate!
carbonate + acid - fizzing and carbon dioxide made!
2HNO3(aq) + CaCO3(s) –> Ca(NO3)2(aq) + H2O(l) + CO2(g)
Ca(NO3)2 is soluble - all nitrates are soluble
CaCO3 is insoluble- all carbonates are insoluble except for Na, K and NH4+
216
What are the products?
H2SO4 + MgCO3 –>
Spot the carbonate + acid?
Think neutralisation with carbon dioxide
H2SO4(aq) + MgCO3(s) –>MgSO4(aq) + H2O(l) + CO2(g)
MgCO3 is insoluble
All Carbonates are insoluble except for Na, K and NH4+
MgSO4 is soluble (aq)
All sulfates are soluble except for Pb and Ba
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Complete the general equation
Metal + Acid –>
Think fizzing
Metal + acid –> salt + hydrogen
The metal must be more reactive than hydrogen in the reactivitiy series (copper, silver, gold and platinum will not react with acid)
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What products will form?
Mg + HCl –>
Think fizzing and spot the hydrogen in the acid- what is left is a salt
Mg(s) +2 HCl(aq) –> MgCl2(aq) + H2(g)
HCl is aqueous- all acids are aqueous
MgCl2 is aqueous- all halides are soluble except for Pb & Ag
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Name the products
Ca + H2SO4 –>
A
Think fizzing and spot hydrogen
Ca(s) + H2SO4(aq) –>CaSO4(aq) + H2(g)
Hydrogen is diatomic- H2
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Name all the diatomic elements
H2 , N2 , O2, Cl2, Br2, I2, F2
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Name the three oxides formed when petrol is burnt in a car engine
Sulfur in fuel reacts with oxygen to form SO2
Nitrogen in air reacts with oxygen to form NO2
Carbon in fuel reacts with air to for CO2
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State two environmental impact of acid rain?
Acid rain lowers the pH of lakes and streams and aquatic life dies
Acid rain leaches minerals from the soil and trees die
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The following occurs in a car engine
Sulfur in fuel reacts with oxygen to form SO2
Nitrogen in air reacts with oxygen to form NO2
Carbon in fuel reacts with air to for CO2
What happens with all these non-metal oxides dissolve in the rain?
Non-metal oxide form acidic solution in water
SO2 –> H2SO4
NO2 –> HNO3
CO2 –> H2CO3
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What is an acid a source of?
Hydrogen ions
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When dissolved in water, acids always produce…
H+ ions
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Acids always contain… in their formula
H
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Bases are known as an ….. if they are soluble in water
alkali
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A base is a …… source
hydroxide ion
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bases are metal ……., metal…….. and metal……
oxides, hydroxides, carbonates
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When dissolved in water bases always produce…
OH- ions
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What is neutralisation?
H+ + OH- -> H2O
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acid + metal ->
salt
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acid + metal oxide ->
salt + water
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acid + metal carbonate ->
salt + water + carbon dioxide
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SNAP =
All sodium, nitrate, ammonium and potassium salts are soluble
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Cl(a)SPbAg =
Chlorides are soluble except for lead and silver
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SolSul CaBaL =
Soluble sulfates except calcium, barium and lead
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InCH =
insoluble carbonates and hydroxides (except for snap salts)
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What is the range of the Ph scale?
0-14
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What is the colour change of the Ph scale from acidic to alkali?
red - orange - green - blue - purple
241
What colour does red litmus turn in the presence of acids and bases?
acid - red
base - blue
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What colour change can you observe in thymolphthalein?
acid - colourless
base - blue
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What colour change can you observe in methyl orange?
acid - red
base - yellow
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Define an acid and an alkali
ACID = A proton or hydrogen donor
ALKALI = A proton or hydrogen accepter
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Difference between an alkali and a base?
Alkali is a base that is soluble in water
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Example of:
1 - Strong acid
2 - Weak acid
3 - Strong alkali
4 - Weak alkali
1 - Stomach acid = HCl (pH 1)
2 - Ethanoic acid (CH3COOH)
3 - Bile (from the gall bladder)
4 - Ammonia, tooth paste
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Weak acid reactions are often what?
Give an example.
They’re reversible.
Ethanoic acid Ethanoate ion + Hydrogen ion
CH3COOH -> CH3COO^- + H^+
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