2.1.4 Acids + 2.1.5 Redox Flashcards
1
Q
what is the formula for ethanoic acid?
A
CH3COOH
2
Q
what is the formula for sodium carbonate?
A
Na2CO3
3
Q
what is the formula for phosphoric acid?
A
H3PO4
4
Q
what is the definition of an acid?
A
in water an acid releases hydrogen ions into solutions (a proton donor)
5
Q
what is the definition of a hydrogen ion?
A
a hydrogen ion has no electrons in its outer shell , it is known as a proton
6
Q
what is the definition of a strong acid?
A
a strong acid releases all of its hydrogen ions in the solution and is completely dissociated / ionised
7
Q
what is the definition of a weak acid?
A
a weak acid only releases a small number of its hydrogen ions in solution and partially dissociates / ionises
8
Q
when a strong acid dissociates is it a reversible reaction?
A
NO
9
Q
when a weak acid dissociates is it a reversible reaction?
A
YES
10
Q
what is the definition of a base?
A
a compound that neutralises an acid, by accepting a hydrogen ion, to form a salt (proton acceptor)
11
Q
what are bases usually?
A
metal oxides or ammonia
12
Q
how do bases form dative covalent bonds?
A
bases donate 2 electrons to the hydrogen ion to form a dative covalent bond
bases can either have a lone pair or negative charge
13
Q
what is the definition of an alkali?
A
an alkali is a soluble base that releases hydroxide ions
14
Q
give examples of common alkalis used
A
hydroxides
NaOH
KOH
Ca(OH)2
15
Q
what is the definition of a salt?
A
a salt is the product of a reaction in which H+ ions from the acid are replaced by the metal or ammonium ions
16
Q
what does a metal + acid make?
A
salt + hydrogen
17
Q
what does a metal oxide (base) + acid make?
A
salt + water
18
Q
what does a metal hydroxide + acid make?
A
salt + water
19
Q
what does a metal carbonate + acid make?
A
salt + carbon dioxide + water
20
Q
what does ammonia + acid make?
A
ammonium salt
21
Q
what is the method for making a standard solution?
A
1 - weigh out the mass of the solid using weigh by difference to 2 decimal places
2 - place the solid into a beaker
3 - add 10cm3 of distilled water to the beaker
4 - stir the solution to dissolve the solid
5 - transfer the solution to a 250cm3 volumetric flask
6 - rinse the equipment into the volumetric flask
7 - make up the solution to the 250cm3 line with distilled water, using a pipette, the bottom of the meniscus should be on the line
8 - put on the lid and invert several times to mix
22
Q
what are concordant results?
A
results within 0.1cm3 of each other
23
Q
what results must you only use in the titration calculation?
A
concordant results
do not use rough
24
Q
what is the equation for the titration calculation?
A
moles = conc x volume
———————-
1000
25
what are the steps for the titration calculation?
1 - moles
2 - ratio
3 - apply to question
26
what is the method for a titration?
1 - rinse all glass wear with distilled water and the solution that will be used
2 - measure 25cm3 of the standard solution with a pipette and filler and put in conical flask
3 - add 3 drops of indicator
4 - place on white tile
5 - using a funnel fill the biurette with acid, to the zero mark with the bottom of the meniscus on this line
6 - complete a rough titration, looking for the end point while swirling the conical flask
7 - repeat the experiment adding the acid drop by drop to reach the endpoint
8 - rinse conical flask between titrations with distilled water
9 - record out titres into a table
10 - calculate the mean titre using concordant results
27
what is uncertainty of a piece of equipment?
half the smallest possible unit you can make
28
what is the equation for percentage uncertainty?
uncertainty of equipment
------------------------------------- X100
size of measurement
29
what do you need to take into account when working out the percentage uncertainty?
how many times you have read off that piece of equipment to get one answer
30
what are steps for the harder titration calculation questions?
1 - read question and draw diagram to understand what is in what equipment
2 - moles
3 - ratio
4 - often moles in volumetric flask
5 - answer question
31
what is a volumetric flask?
a type of laboratory flask, calibrated to contain a precise volume at a particular temperature
32
what are volumetric flasks used for?
precise dilutions and preparation of standard solution
33
what is the equation for new concentration?
original vol
---------------- X original concentration
new vol
34
what is the definition of an oxidation number?
a measure of the number of electrons that an atom uses to bond with an atom of another element
35
what is the oxidation number of a neutral atom?
zero
36
what is the oxidation number of a monatomic atom?
the same as the charge on the ion e.g. O2- = -2
37
what is the sum of all oxidation numbers in a polyatomic ion?
equal to the charge on the ion
38
what is the sum of all oxidation numbers in a neutral compound?
zero
39
what is usually the oxidation state of hydrogen?
+1
40
what is the oxidation state of hydrogen when it is part of a binary metal hydride?
-1
41
what does fluorine always have an oxidation number of in a compound?
-1
42
what is the oxidation number of oxygen usually in a compound?
-2
43
what is the oxidation number of oxygen if it is in a peroxide compound?
-1
44
when does oxygen have an oxidation number of +1?
when bonded to fluorine
45
in what group can oxidation numbers vary?
transition metals
46
what usually are chlorine, bromine and iodine's oxidation numbers?
-1
47
when do halogens not have oxidation number of -1?
when in a compound with oxygen
48
what do we do when a compound needs a systematic name?
write the oxidation number in Roman numerals in brackets after the elements name in a compound
49
what is the definition for redox reaction?
a reaction involving oxidation and reduction
50
what does OIL RIG stand for?
oxidation is loss of electrons
reduction is gaining of electrons
51
what are the two different types of ways of working out a redox reaction?
electron transfer
oxidation numbers
52
what is the rule when working out what is oxidised and reduced in a reaction using oxidation numbers?
if the oxidation number increases it is oxidation
if the oxidation number decreases it is reduction
53
what do you have to write in your answer when working out what is oxidised and reduced in a reaction?
state the element and how the oxidation number has changed and what it has changed from
54
what is the reaction called if the same element is oxidised and reduced?
disproportination
55
What is the ideal gas equation?
PV = nRT
## Footnote
P = Pressure, V = Volume, n = moles, R = 8.31 JK-1mol-1, T = Temperature in Kelvin
56
What are the units for Pressure (P) in the ideal gas equation?
Pa
57
What are the units for Volume (V) in the ideal gas equation?
m³
58
What are the units for Temperature (T) in the ideal gas equation?
K
59
What is the value of R in the ideal gas equation?
8.31 JK-1mol-1
60
How do you convert temperature from Celsius to Kelvin?
Add 273
61
Convert 20°C to Kelvin.
293 K
62
Convert 500 cm³ to m³.
0.0005 m³
63
Calculate the moles of gas using the ideal gas equation.
moles = PV/RT
64
What is the mass of Cl gas given a pressure of 100 kPa, temperature of 20°C, and volume of 500 cm³?
1.46 g
65
Calculate the molar mass (Mr) of a volatile liquid if 0.150 g is injected into a gas syringe at 70°C and 100 kPa with a volume of 80 cm³.
53.4 g mol-1
66
What are potential errors when using a gas syringe?
* Gas escapes before bung inserted
* Syringe sticks
* Some gases are soluble in water
67
What is the molar gas volume at room temperature and pressure?
24 dm³
68
How can the pressure of a gas mixture in a flask be calculated?
Use P1V1 = P2V2
69
True or False: Equal volumes of any gases contain equal numbers of molecules under the same conditions of temperature and pressure.
True
70
What is the total volume of gases produced when 500 cm³ of CO reacts with 500 cm³ of NO?
750 cm³
71
Calculate the volume of oxygen needed to react with 500 cm³ of methane.
1000 cm³
72
Fill in the blank: The volume of a gas depends on _______ and _______.
[pressure], [temperature]
73
What does an acid release in aqueous solution?
H+ ions
74
What are the most common strong acids?
* Hydrochloric (HCl)
* Sulfuric (H2SO4)
* Nitric (HNO3)
75
What is a weak acid example?
Ethanoic acid (CH3COOH)
76
How is a Bronsted-Lowry acid defined?
As a proton (H+) donor
77
What is the definition of a base?
Substances that neutralise acids
78
What are common bases?
* Metal oxides
* Metal hydroxides
* Ammonia
79
How is a Bronsted-Lowry base defined?
As a proton (H+) acceptor
80
What is an alkali?
A soluble base that releases OH- ions in aqueous solution
81
What are the most common alkalis?
* Sodium hydroxide (NaOH)
* Potassium hydroxide (KOH)
* Aqueous ammonia (NH3)
82
What happens when a base accepts H+ ions?
It forms water (H2O)
83
What is the difference between strong and weak acids?
* Strong acids completely dissociate in water
* Weak acids only slightly dissociate
84
What is formed in a neutralisation reaction?
Salts
85
How is a salt formed?
When the H+ ion of an acid is replaced by a metal ion or an ammonium ion
86
What is the general equation for a neutralisation reaction?
ACID + BASE → SALT + WATER
87
What is produced in acid and carbonate reactions?
Salt, Water, and Carbon Dioxide
88
What indicates effervescence in carbonate reactions?
CO2 gas evolved
89
What are the safety precautions for conducting titrations?
* Rinse equipment
* Wear eye protection and gloves
* Wash affected parts after spillage
90
What is the purpose of using indicators in titrations?
To observe colour change at the end point
91
What color change does phenolphthalein indicate?
Pink (alkali) to colourless (acid)
92
What color change does methyl orange indicate?
Yellow (alkali) to red (acid)
93
What should be done if the jet space in the burette is not filled properly?
It can lead to errors in titre readings
94
What is required for titration results to be considered accurate and repeatable?
Two concordant results within 0.1 cm³ of each other
95
What should be recorded during a titration?
* Initial and final readings
* Titre volumes to 2 decimal places
96
What is the effect of adding distilled water during a titration?
It washes acid into the reaction mixture without affecting the titration reading
97
What are common titration equations?
* CH3COOH + NaOH → CH3COO-Na+ + H2O
* H2SO4 + 2NaOH → Na2SO4 + 2H2O
* HCl + NaOH → NaCl + H2O
98
What should be considered when titrating a mixture?
Whether the mixture contains other substances with acid-base properties
99
Why are sodium hydrogen carbonate and calcium carbonate used for neutralising excess acid?
They are not corrosive and have no toxicity
100
What is a suitable substance for dealing with excess stomach acid?
Magnesium hydroxide
101
True or False: Acids and alkalis are corrosive.
True
102
What is the definition of 'Readings' in the context of measurements?
The values found from a single judgement when using a piece of equipment.
103
How are 'Measurements' defined?
The values taken as the difference between the judgements of two values.
104
What is the sensitivity uncertainty for a 3 d.p. balance?
+ 0.001 g.
105
What is the sensitivity uncertainty for a volumetric flask?
+ 0.1 cm3.
106
What is the sensitivity uncertainty for a 25 cm pipette?
+ 0.1 cm3.
107
What is the sensitivity uncertainty for a burette?
+ 0.10 cm3.
108
How do you calculate percentage error for a piece of equipment?
% uncertainty = (uncertainty / measurement made on apparatus) × 100.
109
What is the formula to calculate % uncertainty for a burette?
% uncertainty = 0.10 / average titre result × 100.
110
What is the method to find the maximum percentage apparatus uncertainty?
Add all the individual equipment uncertainties together.
111
What is the uncertainty for an analogue scale reading?
At least ±0.5 of the smallest scale reading.
112
What is the uncertainty for an analogue scale measurement?
At least ±1 of the smallest scale reading.
113
What is the uncertainty for a digital scale?
± the resolution of the apparatus in each measurement.
114
What is the uncertainty of a measurement using a burette during titration?
+/- 0.10 cm3 for two readings.
115
How can uncertainties in a titration be reduced?
Replace measuring cylinders with pipettes or burettes.
116
What effect does increasing the titre volume have on % uncertainty?
It reduces the % uncertainty in a burette reading.
117
How can you decrease apparatus uncertainties?
* Decrease the sensitivity uncertainty by using apparatus with greater resolution
* Increase the size of the measurement made.
118
In an investigation, which measurements have the highest experimental uncertainties?
The experiments with the smallest readings.
119
How can you reduce % uncertainty in weighing a solid?
Use a balance that measures to more decimal places or use a larger mass.
120
What is the method for calculating the percentage difference between actual and calculated values?
% = (difference / actual value) × 100.
121
If the calculated Mr is 203 and the real value is 214, what is the % difference?
% = (11 / 214) × 100 = 5.41%.
122
What does it indicate if the % uncertainty due to the apparatus is less than the percentage difference?
There is a discrepancy in the result due to other errors.
123
What does it indicate if the % uncertainty due to the apparatus is greater than the percentage difference?
There is no discrepancy and all errors can be explained by the sensitivity of the equipment.
124
What is the process of electron loss called?
Oxidation
## Footnote
Oxidation involves an increase in oxidation number.
125
What happens to the oxidation number during oxidation?
It increases
## Footnote
Oxidation is characterized by electron loss.
126
What is the oxidation number of all uncombined elements?
Zero
## Footnote
This is one of the rules for assigning oxidation numbers.
127
What do the oxidation numbers of the elements in a compound add up to?
Zero
## Footnote
This follows the rules for determining oxidation numbers.
128
What is the oxidation number of a monoatomic ion equal to?
The ionic charge
## Footnote
This is a rule for assigning oxidation numbers.
129
In a polyatomic ion, what does the sum of the individual oxidation numbers equal?
The charge on the ion
## Footnote
This helps determine oxidation numbers in complex ions.
130
What is the oxidation number of Group 1 metals?
+1
## Footnote
This is a specific rule for oxidation numbers.
131
What is the oxidation number of Group 2 metals?
+2
## Footnote
This is part of the rules for assigning oxidation numbers.
132
What is the oxidation number of Aluminum (Al)?
+3
## Footnote
This is a specific rule for oxidation numbers.
133
What is the oxidation number of hydrogen (H) in most compounds?
+1
## Footnote
Except in metal hydrides where it is -1.
134
What is the oxidation number of fluorine (F)?
-1
## Footnote
This is a fixed oxidation number for fluorine.
135
What is the process of electron gain called?
Reduction
## Footnote
Reduction involves a decrease in oxidation number.
136
What happens to the oxidation number during reduction?
It decreases
## Footnote
Reduction is characterized by electron gain.
137
What is the oxidation number of sodium (Na) in NaCl?
+1
## Footnote
The chloride ion (Cl) has an oxidation number of -1.
138
What is the oxidation number of chlorine (Cl) in NaCl?
-1
## Footnote
The oxidation numbers in NaCl sum to zero.
139
What is the oxidation number of carbon (C) in CO3^2-?
+4
## Footnote
The carbonate ion has overall charge of -2.
140
What is the oxidation number of oxygen (O) in CO3^2-?
-2
## Footnote
There are three oxygen atoms contributing to the charge.
141
How do you find the oxidation number of an element with variable oxidation states?
Use oxidation number rules
## Footnote
This includes the rules for summing to zero or the charge.
142
What is the oxidation number of chlorine (Cl) in CaCl2?
-1
## Footnote
There are two Cl atoms, each with an oxidation number of -1.
143
What Roman numeral indicates the oxidation state of an element?
Magnitude of oxidation state
## Footnote
Used to clarify ambiguous names in compounds.
144
What is the name of FeCl2?
Iron(II) Chloride
## Footnote
The Roman numeral indicates the +2 oxidation state of iron.
145
What is the name of FeCl3?
Iron(III) Chloride
## Footnote
The Roman numeral indicates the +3 oxidation state of iron.
146
What is the oxidation state of sulfur in K2SO4?
+6
## Footnote
The oxidation state is indicated in the compound's name.
147
Fill in the blank: NaClO is named __________.
Sodium chlorate(I)
## Footnote
The Roman numeral indicates the oxidation state of chlorine.
148
Fill in the blank: K2SO4 is named __________.
Potassium sulfate(VI)
## Footnote
The Roman numeral indicates the oxidation state of sulfur.
149
Fill in the blank: NaNO2 is named __________.
Sodium nitrate(III)
## Footnote
The Roman numeral indicates the oxidation state of nitrogen.
150
Fill in the blank: NaNO3 is named __________.
Sodium nitrate(V)
## Footnote
The Roman numeral indicates the oxidation state of nitrogen.
151
What do metals generally do in redox reactions?
Metals generally form ions by losing electrons with an increase in oxidation number to form positive ions.
## Footnote
Example: Zn → Zn2+ + 2e-
152
What happens to the oxidation number of oxygen in redox reactions?
Oxygen is reducing because its oxidation number is decreasing from 0 to -2.
## Footnote
Example: 4Li + O2 → 2Li2O
153
How do non-metals typically react in redox reactions?
Non-metals generally react by gaining electrons with a decrease in oxidation number to form negative ions.
## Footnote
Example: Cl + 2e → 2Cl-
154
What is the change in oxidation number for tungsten in the reaction WO3 + 3H2 → W + 3H2O?
Tungsten is reducing because its oxidation number is decreasing from +6 to 0.
## Footnote
Oxidation states: +6 to 0
155
What is the oxidation change for lithium in redox reactions?
Lithium is oxidising because its oxidation number is increasing from 0 to +1.
## Footnote
Example: 2Li → 2Li+ + 2e-
156
What is the change in oxidation number for nitrogen in redox reactions?
Nitrogen is reducing because its oxidation number is decreasing from +5 to +4.
## Footnote
Example: 2Sr(NO3)2 → 2SrO + 4NO2 + O2
157
What happens to hydrogen's oxidation number in redox reactions?
Hydrogen is oxidising because its oxidation number is increasing from 0 to +1.
## Footnote
Example: 2NH3 + NaClO → N2H4 + NaCl + H2O
158
What is the change in oxidation number for chlorine in redox reactions?
Chlorine is reducing because its oxidation number is decreasing from +1 to -1.
## Footnote
Example: 2NH3 + NaClO → N2H4 + NaCl + H2O
159
How does oxygen behave in redox reactions?
Oxygen is oxidising because its oxidation number is increasing from -2 to 0.
## Footnote
Not all oxygen atoms change oxidation number in every reaction.
160
What is the general reaction format for metals reacting with acids?
ACID + METAL → SALT + HYDROGEN.
## Footnote
Example: 2HCl + Mg → MgCl2 + H2
161
What is the oxidation change for hydrogen in the reaction 2HCl + Mg → MgCl2 + H2?
Hydrogen is reducing because its oxidation number is decreasing from +1 to 0.
## Footnote
Oxidation states: +1 to 0
162
What is the oxidation change for magnesium in reactions with acids?
Magnesium is oxidising because its oxidation number is increasing from 0 to +2.
## Footnote
Example: Mg → Mg2+ + 2e-
163
What is the oxidation change for nitrogen in redox reactions?
Nitrogen is oxidising because its oxidation number is increasing from -3 to -2.
## Footnote
Example: In reactions with strong oxidisers.
164
What observable effect occurs when metals react with hydrochloric acid?
These reactions will effervesce because H2 gas is evolved and the metal will dissolve.
## Footnote
Example: Fe + H2SO4 → FeSO4 + H2
