chemical changes (seneca) Flashcards
1
Q
Acids are substances that —– when they dissolve in water (aqueous solutions).
A
form hydrogen (H+) ions
2
Q
Acids are substances that form hydrogen (H+) ions when they …
A
dissolve in water (aqueous solutions).
3
Q
Alkalis are substances that form —— when they dissolve in water (aqueous solutions).
A
hydroxide (OH-) ions
4
Q
Alkalis are substances that form hydroxide (OH-) ions when
A
they dissolve in water (aqueous solutions)
5
Q
The pH scale is used to measure …
A
how acidic or alkaline a substance is.
6
Q
Acids and alkalis are on the opposite ends of the ——. They combine to form —— , which is…
A
pH scale
water
neutral.
7
Q
hydrogen ion+hydroxide ion=
A
water
8
Q
——- ion+——- ion=water
A
hydrogen
hydroxide
9
Q
An oxidation reaction involves gaining …
A
oxygen
10
Q
Oxidation reactions can also involve losing…
A
electrons.
11
Q
When metals react with oxygen, …
A
metal oxides are produced
12
Q
A reduction reaction involves losing…
A
oxygen
13
Q
A reduction reaction involves ——oxygen
A
losing
14
Q
Oxidation reactions can also involve —- electrons.
A
losing
15
Q
when metal oxides lose oxygen,
A
they return to their atomic form
16
Q
A mnemonic (memory aid) for remembering what happens to electrons during oxidation and reduction reactions is
A
OIL RIG
17
Q
Metals reacting with oxygen to form metal oxides is an example of
A
an oxidation reaction
18
Q
When reacting with other substances, metal atoms always form …
A
positive ions.
19
Q
The reactivity of a metal is linked to …
A
how easy it is for a metal to form its positive ion.
20
Q
highly unreactive metals are found in …
A
the Earth’s crust as pure metals.
21
Q
highly unreactive,pure metals that are found in the Earth’s crust are also called
A
native metals.
22
Q
A metal can only displace another metal from a compound if
A
it is located above it in the reactivity series.
23
Q
1 reactive substances can displace (replace) 2 reactive substances from compounds.
A
1.More
2.less
24
Q
what does spectator ions mean?
A
ions that are unchanged in the reaction
25
Potassium, sodium and lithium all react quickly with cold water to produce
a metal hydroxide and hydrogen gas.
26
Potassium, sodium and lithium all react quickly with -------- to produce a metal hydroxide and hydrogen gas.
cold water
27
Potassium reacting with cold water is the 1. so reacts 2.The hydrogen produced 3. and the metal also sets alight, sparking and burning with a 4.
1.most reactive
2.very quickly
3.ignites instantly
4.lilac flame.
28
Sodium, when reacting with cold water, 1. and 2. that 3.
1.fizzes rapidly
2.melts to form a ball
3.moves around on the water surface.
29
Lithium,when reacting with cold water, 1. and 2., becoming 3.
1.fizzes steadily
2. floats
3.smaller until it eventually disappears.
30
The metals that react with dilute acids but not cold water are...
magnesium, aluminium, zinc, iron and lead (iron and lead react slowly).
31
Metals don't have to be ------ to react with dilute acids.
that reactive
32
The only metals that aren't reactive enough,to react with dilute acids, are ...
copper, silver, gold and platinum.
33
Most metals react with dilute acids to give...
a salt (e.g. aluminium chloride) and hydrogen gas.
34
Reducing a metal with carbon will result in the ...
extraction of the metal if the metal is lower in the reactivity series than carbon.
35
Most metals are only found as 1. because the metal has 2. Because of this,3...
1.compounds
2.reacted with other elements in the past
3. the metal has to be extracted from the ore (rock) where the metal compound is found.
36
In the reduction, the metal oxide ----- oxygen to form a pure metal.
loses
37
Reduction with carbon normally involves 1, which is often used in the form of 2.
1.heating the metal oxide in the presence of the carbon
2.coal
38
Carbon is used in reduction because it is...
cheap and abundant
39
What form is carbon often used in when reducing metal oxides?
Coal
40
Potassium down to aluminium are more reactive than carbon and so ...
cannot be extracted by reduction with carbon.
41
Silver, gold and platinum are either found as --------- or can be ...
natural elements
simply extracted by heating directly in air
42
The remaining metals - zinc, iron, and copper - are all commonly extracted by ...
reduction with carbon.
43
What are the metals that react with dilute acids but not cold water?
lead
aluminium
iron
magnesium
zinc
44
In a reduction reaction with carbon, a metal oxide loses ----- to form a pure metal.
oxygen
45
Reducing a metal with carbon will result in the extraction of the metal if the metal is ------- in the reactivity series.
lower
46
what metals that can't react with dilute acids?
-platinum
-copper
-silver
-gold
47
When zinc is reacted with calcium carbonate, no reaction occurs. Explain why.
Zinc does not react with calcium carbonate because zinc is not as reactive as calcium.
48
Metal + Acid ->
Salt + Hydrogen
49
what is the chemical formula of calcium
Ca 2+
50
what is the chemical formula of carbonate
CO3 2-
51
what is the chemical formula of sodium
Na +
52
what is the chemical formula of bromide
Br -
53
what is the chemical formula of sulfate
SO4 2-
54
what is the chemical formula of chloride
Cl-
55
what is the chemical formula of hydrochloride acid?
HCl
56
Redox reactions involve ...
a reduction reaction (one reactant gains electrons) and an oxidation reaction (one reactant loses electrons).
57
Spectator ions are not present in the ...
ionic equations
58
what is the acronym for what happens during oxidation and reduction reactions?
Oxidation
Is
Loss (of electrons)
Reduction
Is
Gain (of electrons)
59
Reactions that involve both a reduction and oxidation are called ...
redox reactions
60
Acids can be neutralised by ...
reacting with bases (an alkali is a base that dissolves in water)
61
Metal carbonates, metal oxides and metal hydroxides are all examples of ...
bases.
62
------------------------------ are all examples of bases.
Metal carbonates, metal oxides and metal hydroxides
63
Acid + carbonate →
salt + water + carbon dioxide
64
Acid + hydroxide →
salt + water
65
Acid + metal oxide →
salt + water
66
magnesium carbonate+nitric acid→
magnesium nitrate+carbon dioxide+water
67
When acids are neutralised by metal carbonates, what is formed?
salt + water + carbon dioxide
68
when the acid Hydrochloric acid becomes a salt it becomes
Chloride
69
when the acid nitric acid becomes a salt it becomes
nitrate
70
when the acid sulfuric acid becomes a salt it becomes
sulfate
71
What is the name given to ions that remain unchanged during redox reactions, and aren't included in the ionic equation?
Spectator ions
72
Soluble salts are ...
salts which dissolve in water.
73
We can produce soluble salts through a reaction between ...
acids and solid, insoluble substances
such as pure metals, metal oxides, metal hydroxides, or metal carbonates.
74
What must be reacted together to produce a soluble salt?
- Solid, insoluble substance
- acid
75
what is a word that means 'does not dissolve in water'
insoluble
76
what is a word that means 'dissolves in water'
soluble
77
The aim of Required Practical - Separating Mixtures is to produce ...
a pure, dry sample of a soluble salt from an insoluble oxide or carbonate.
78
what does preparation entail for Required Practical - Separating Mixtures
Use a Bunsen burner to gently warm the acid.
Add the insoluble solid (with stirring) until the reaction no longer happens.
79
what does filtration entail for Required Practical - Separating Mixtures
Filter the solution to remove the excess insoluble solid.
This will leave a solution of the salt dissolved in water.
80
what does crystallisation entail for Required Practical - Separating Mixtures
-Heat the solution in an evaporating basin above a beaker of water.
-The 'water bath' ensures gentle heating.
-Let the solution cool and allow more water to evaporate.
-As water evaporates, the solution will become more concentrated and the salt will begin to crystallise.
81
Crystallisation separates a ...
dissolved solid (the solute) from a liquid (the solvent)
82
what method do you use to separate a mixture of insoluble solid and liquid?
filtration
83
what method do you use to separate a Mixture of soluble solid and liquid (solution)
crystallisation
84
what method do you use to separate a Mixture of liquids
-Simple distillation
-Fractional distillation
85
what method do you use to separate a Mixture of dissolved solids
Chromatography
86
Double displacement reactions are
reactions in which two chemical substances react by exchanging ions to produce two new molecules.
87
what are the steps for crystallisation
1.Heat the solution in an evaporating basin above a bunsen burner.
2.The 'water bath' ensures gentle heating.
3.Leave the solution to cool and allow more water to evaporate.
4.As water evaporates, the solution will become more concentrated and the salt will begin to crystallise.
88
The acidity or alkalinity of a solution is measured using the -----, which ranges from 0 to 14.
pH scale
89
The acidity or alkalinity of a solution is measured using the pH scale, which ranges from ...
0 to 14.
90
pH of exactly 7 is a
neutral
91
pH less than 7 is a ...
acid
92
Strong acids have a pH close to ...
0
93
Acids form ------ when they dissolve in water.
hydrogen (H+) ions
94
Acids form hydrogen (H+) ions when they ...
dissolve in water.
95
pH more than 7 is a ...
alkali
96
Strong alkalis have a pH close to ...
14.
97
Alkalis form hydroxide (OH-) ions when they ...
dissolve in water.
98
Alkalis form ------ when they dissolve in water.
hydroxide (OH-) ions
99
whats an example of an acid?
acid rain
100
whats an example of a neutral?
pure water
101
whats an example of an alkaline?
washing-up liquid
102
Universal indicator changes to a particular ...
colour depending on the pH of a solution.
103
A pH probe returns a ----- that represents the pH of a solution.
number
104
The numerical pH scale is a measure of the ...
For every increase of - in pH, the --------- gets ...
concentration of H+ ions in a solution.
1
concentration of H+ ions
divided by 10:
105
At pH 0, the concentration of H+ ions is
1 mol/dm3.
106
At pH 1, the concentration of H+ ions is
0.1 mol/dm3.
107
At pH 2, the concentration of H+ ions is
0.01 mol/dm3.
108
Increase pH by 1 →
divide H+ concentration by 10
109
Red cabbage contains a chemical called ...
anthocyanin.
110
Red cabbage act as ...
natural litmus paper.
111
Red cabbage molecules change ------- in acidic or alkaline conditions and this changes...
shape
the molecules' colour.
112
A neutralisation reaction happens when ...
an alkali is reacted with an acid
113
The 1 from the acid combine with 2 from the alkali to give 3.
1.hydrogen ions
2.hydroxide ions
3.water
114
A ---------- reaction happens when an acid reacts with an alkali
neutralisation
115
Titration is a technique that measures ...
the volumes of acid and alkali solutions that are needed in a neutralisation reaction.
116
If, for example, we were neutralising an alkali with an acid, titration could be used to calculate the concentration of the alkali if we knew:
1.The concentration of the acid to be added.
2.The volume of the alkali.
117
Indicators show the end point of titrations by...
suddenly changing colour when the solution turns from acidic to alkaline, or alkaline to acidic.
118
When choosing an indicator, the strength of the acid and alkali must be considered.
If both the acid and alkali are strong, suitable indicators would be:
Methyl orange (yellow in alkali → red in acid).
Phenolphthalein (pink in alkali → colourless in acid).
119
in a titration, we gradually add the acid to the alkali until the ...
indicator changes colour
120
All acids ionise (become ions) in ...
aqueous solutions
121
All acids -------- in aqueous solutions
ionise (become ions)
122
The strength of an acid is determined by...
how much it ionises in water.
123
Strong acids fully ionise in water, meaning that ...
all of the acid molecules break up to form H+ ions.
124
give three examples of strong acids
hydrochloric acid
Sulfuric acid
nitric acid
125
when ionising in hydrochloric acid (strong acid) produce the equation
HCl →
H+ + Cl-
126
Weak acids 1 ionise in water, meaning that ...
1.only partially
not all of the acid molecules break up to form H+ ions.
127
when ionising in water ethanoic acid (weak acids) produce the equation
CH3COOH ⇌
CH3COO- + H+
128
-------- are weak acids.
Most acids
129
what colour does the indicator phenolphthalein?
pink
130
What ions are formed when acids ionise?
H+
131
When ionic compounds are melted or dissolved in water,
the ions (charged particles that have gained/lost electrons) are free to move around, and the liquid/solution will conduct electricity.
132
Ionic compounds that dissolve in water to make a solution that conducts electricity are called ...
electrolytes.
133
what are electrolytes?
Ionic compounds that dissolve in water to make a solution that conducts electricity
134
When a voltage (direct current) is applied across an electrolyte, ...
the charged ions are attracted to the electrode with the opposite charge to the ion.
135
Positively charged ions are attracted to ...
the negative electrode (cathode).
136
Negatively charged ions are attracted to ...
the positive electrode (anode).
137
another name for a positive electrode is...
anode
138
another name for a negative electrode is...
cathode
139
When an ion touches an electrode,
electrons can be transferred, producing elements.
140
If copper ions (Cu2+) are in a solution and a voltage is applied,-------
When they touch the cathode, each Cu2+ ion will ...
they'll move to the cathode (negative electrode)
gain 2 electrons and form a copper metal.
141
What happens when ionic compounds are dissolved in water?
The charged ions become free to move
The liquid/solution will conduct electricity
142
Since non-metals ions are ------ (anions), they will be ------ to the ------------(anode), .......
negative
attracted
positive electrode
where the non-metal (element) will form
143
Since metals ions are ----- (cations), they will be ------ to the -----(cathode), ...
positive
attracted
negative electrode
where the metal (element) will form
144
the metal and non-metal ions within the molten ionic compound become ...
free to move so the liquid can undergo electrolysis
145
Positive metal ions are called cations. They are always attracted to the ...
cathode
146
Positive metal ions (cations) are attracted to ...
negative electrode (cathode)
147
Negative non-metal ions (anions) are attracted to ...
positive electrode (anode)
148
Electrolysis is the process that
splits ionic compounds into the different elements that they are made of.
149
Electrolysis happens using a solution that ...
conducts electricity.
150
Electrolysis is used to ...
extract reactive metals from molten ores (melted materials containing metals)
151
Electrolysis is used to ...
extract metals such as aluminium, which are higher in the reactivity series than carbon.
152
What happens at the anode? (Extracting Metals)
Oxygen forms at the carbon anode. The carbon and oxygen react to give carbon dioxide.
The anode is usually made of carbon because it is a good conductor and is cheap.
153
(Extracting Metals)Oxygen forms at the 1. The carbon and oxygen react to give 2.
1.carbon anode
2.carbon dioxide.
154
What happens at the cathode? (Extracting Metals)
The element is formed at the cathode.
155
The anode is usually made of carbon because it is a 1. and is 2.
1.good conductor
2.cheap
156
Electrolysis is a process in which
electrical energy, from a direct current (dc) supply, breaks down electrolytes
157
What are the disadvantages of electrolysis?
-Lots of energy is needed to:
Melt the solid ionic compound to allow the ions to flow.
Produce the electrical current.
-expensive
158
Electrolysis is used to extract reactive
1. from 2.
metals
molten ores
159
how would you extract a metal that is less reactive than carbon and less reactive than copper
Found as natural element
Heat directly in air
160
how would you extract a metal that is less reactive than carbon and more reactive than copper
Reduction with carbon
161
how would you extract a metal that is More reactive than carbon
Electrolysis
162
Which ions are attracted to which electrode?
cations -> cathode
anions-> anode
163
When a 1 is applied across an electrolyte, the charged ions are attracted to the oppositely charged 2.
1. voltage
2.electrode
164
What aspects of using electrolysis to extract metals require lots of energy?
-providing the electrical current
-melting the solid ionic compound
165
2 ------- are submerged in an electrolyte, and a ...
electrodes
voltage is applied across the electrodes using a power supply.
166
Electrolysis requires large amounts of ---- to melt the solid ionic compound and to provide the -----
energy
electrical current
167
The products of the electrolysis of aqueous solutions are difficult to predict because ...
the water molecules in the solution split up to give hydrogen (H+) and hydroxide (OH-) ions.
168
What is formed at the cathode depends on the ------ of the metal
reactivity
169
At the cathode (negative electrode) (electrolysis of aqueous Solutions), ------- is produced if the metal is higher than hydrogen in the reactivity series.
hydrogen
170
At the cathode (negative electrode) (electrolysis of aqueous Solutions), ------- is produced if the metal is lower than hydrogen in the reactivity series.
the metal
171
At the anode (positive electrode) ,(electrolysis of aqueous Solutions),If there are halide ions present, ...
the respective halogen forms.
172
What is formed at the anode depends on if there are ...
halide ions present
173
At the anode (positive electrode) ,(electrolysis of aqueous Solutions), if there are no halide ions, ...
oxygen forms
174
An aqueous solution of copper(II) sulfate (CuSO4) contains Cu2+, SO42-, H+ and OH- ions. What happens when it is electrolysed?
At the anode, oxygen is produced as there are no halide ions present:
4OH- → O2 + 2H2O + 4e-
At the cathode, copper is produced as it is lower in the reactivity series than hydrogen:
Cu2+ + 2e- → Cu
175
During electrolysis, different reactions take place ...
at the different electrodes
176
The reactions that happen at each electrode can be shown using ...
half equations
177
At the cathode (negative electrode), ----- reactions happen i.e. ...
Reduction
positively charged ions gain electrons
178
At the anode (positive electrode), ------ reactions happen i.e. ...
oxidation
negatively charged ions lose electrons
179
Half equations are ...
equations that show one-half of a redox reaction.
180
A redox reaction is a reaction in which ...
both oxidation and reduction occur
181
2Br − →Br 2+2e −
In the electrolysis of lead bromide, ...
bromide ions are oxidised at the anode to give bromine and electrons.
182
at the anode, -------- reactions takes place
oxidation
183
at the cathode, ------- reactions takes place
reduction
184
In the electrolysis of aqueous solutions, what products can form at the anode?
Oxygen gas
A halogen
185
the product formed at the anode depends on on wether there's
a halide ions present or absent
186
the product formed at the cathode depends on whether the metal involved is
more reactive or less reactive than hydrogen
187
What region of the pH scale would a substance that forms H+ be on?
red 1 or 2
188
Which substances would be in the purple region of the pH scale?
bases
alkali
189
what characteristic makes a metal react easily
a metal that produces a positive ion more easily
190
Give 2 reasons why carbon is used to extract metals from their oxides
Carbon is cheap
Carbon is abundant
191
not all acids break up to realease...
H+
