Module 2 Foundations In Chemistry Flashcards
1
Q
What was stated in Dalton’s atomic theory? (4)
A
- Atoms are tiny particles made of elements
- Atoms cannot be divided
- All the atoms in a element are different to those of other elements
2
Q
What did Thompson discover about electrons? (3)
A
- They have a negative charge
- They can be deflected by magnet and electric field
- They have very small mass
3
Q
Explain the plum pudding model
A
Atoms are made up of negative electrons moving around in a sea of positive charge
4
Q
What were Rutherford’s proposal after the gold leaf experiment? (4)
A
- Most of the mass and positive charge of the atom are in the nucleus
- Electron orbit the nucleus
- most of atom’s volume is the space between the nucleus and the electrons
- Overall positive and negative charges must balance
5
Q
Explain the current model of the atom
A
- Protons and neutrons are found in the nucleus
- Electrons orbit in shells
- Nucleus is tiny compared to the total volume of atom
- Most of atom’s mass is in the nucleus
- Most of the atom is empty space between the nucleus and the electrons
6
Q
What are the charges of :
A proton
A neutron
An electron
A
Proton: +1
Electron: -1
Neutron: 0
7
Q
What are the masses of:
Proton
Neutron
Electron
A
Proton: 1
Neutron: 1
Electron: 1/1380
8
Q
What letter represents the atomic number of an atom?
A
Z
9
Q
What does the atomic number tell you?
A
Atomic number = number of protons in an atom
10
Q
Which letter represents the mass number?
A
A
11
Q
How is mass number calculated?
A
Mass number = number of protons + neutrons
12
Q
How to calculate number of neutrons
A
Number of neutrons = mass number of- atomic number
13
Q
What are isotopes?
A
Atoms of the same element with different number of neutrons
14
Q
Why does different isotopes of the same element react in the same way? (2)
A
- Neutrons have no impact on the chemical reactivity
- Reactions involve electrons, isotopes have the same number of electrons in the same arrangement
15
Q
What are ions?
A
Charged particles that are formed when an atom loses or gains electrons
16
Q
What is the charges of of the ion when electrons are gained?
A
Negative
E.g 2+ ion has lost 3 electrons
17
Q
What is the unit used to measure atomic masses called?
A
Unified atomic mass unit, u
18
Q
Define relative atomic mass
A
The weighted mean mass of an atom of an element compared with 1/12 of the mass of an atom of carbon-12
19
Q
What is the unit of relative atomic mass?
A
No units
20
Q
Define relative isotopic mass
A
The mass of an atom of an isotope compared with 1/12 of the mass of an atom of carbon-12
21
Q
The relative isotopic mass is same as which number?
A
Mass number
22
Q
What 2 assumptions are made when calculating mass number?
A
- Contribution of the electron is neglected
- Mass of both proton and is taken as 1.0 u
23
Q
How to calculate the relative molecular mass and relative formula mass?
A
Both can be calculated by adding the relative atomic masses of each of the atom making up the molecules or the formula
24
Q
What are the uses of mass spectrometry? (3)
A
- Identify unknown compounds
- Find relative abundance of each isotope of an element
- Determine structural information
25
How does a mass spectrometer work?
- Sample is made into positive ions
- They pass through the apparatus and are separated according to mass to charge ratio
- A computer analyses the data and produces mass spectrum
26
How is the group number related to the number to electrons?
Group number = number of electrons in the outer shell
27
Does the group number indicates horizontal or vertical column in the periodic table?
Vertical column
28
Do metals usually gain or lose electrons?
Lose electrons
(Non metals usually gain electrons)
29
Which are the 4 elements that don’t tend to form ions and why?
Beryllium (Be)
Boron (B)
Carbon (C)
Requires a lot of energy to transfer outer shell electrons
30
What are molecular ions?
Covalently bonded atoms that lose/gain electrons
31
What is the charge of an ammonium ion?
+1 —> NH4+
32
What is the charge of a hydroxide ion?
-1
OH-
33
What is the charge of a nitrate ion?
-1
NO3-
34
What is the charge of a carbonate ion?
-2
Co3 2-
35
What is the charge of an sulphate ion?
-2
So4 2-
36
What is the empirical formula?
Simplest whole number ratio of atoms of each element present in a compound
37
How to calculate empirical formula?
- divide the amount of each element by its molar mass
- divide the answers by the smallest value obtained
- If there is a decimal, divide by a suitable number to make it into a whole number
38
What is the symbol for amount of substance?
n
39
What is the unit used to measure amount if substance?
Mole
40
What does the Avogadro constant represent?
The number of atoms per mole of the carbon-12 isotope
41
How to calculate the mass of 1 mole of the element?
Mass of 1 mole = relative atomic masses in grams
42
How to calculate moles when mass and molar mass are given?
Moles (mol) = mass (g) / molar mass (gmol-1)
43
State Avogadro’s law
Under the same temperature and pressure, one mole of any gas would occupy the same volume
44
How much volume does a gas occupy, at room temperature and pressure?
24 dm3 or 24000 cm3
45
Define molar gas volume
The volume per mole of gas molecules
46
Why do different gas particles occupy the same volume?
The gas particles are very spread out, individual differences has no effect
47
How to calculate moles when gas volume is given?
Moles (mol) = volume (dm3) / 24
Or
Moles (mol) = volume (cm3) / 24000
48
What are the ideal ways in which gases behave? (5)
- in continuous motion
- no intermolecular forces experienced
- exert pressure when they collide with each other of container
- no KE is lost in the collisions
- when temp increases, KE of gases also increase
49
What is the ideal gas equation?
pV = nRT
Pressure x volume = number of moles x gas constant x temperature
50
1 atmospheric pressure is equal to how many pascal?
1 atm =101325 Pa
51
0°C is equal to how many kelvin?
273K
52
What does concentration of a solution mean?
It is the amount of solute dissolved in 1 dm3 of solvent
53
How to calculate moles when concentration and volume are given?
Moles = concentration x volume
54
What is a standard solution?
A solution of known concentration
55
What are the steps to prepare a standard solution?
1. Weight the solitude by weighing by difference
2. In a beaker dissolve the solute using the solvent
3. Pour the solution into a volumetric flask
4. Rinse the beaker using the solution and add it to the flask
5. Add solvent to the flask carefully until it reaches the graduation line
6. Mix the solution thoroughly to ensure complete mixing
56
What does the terms concentrated and dilute mean?
Concentrated - large amount of solute per dm3 of solvent
Dilute - small amount of solute per dm3 of solvent
57
What is a species in a chemical reaction?
Any particle that takes part in a reaction
58
What are the 4 common state symbols?
1. Solid
2. Liquid
3. Gaseous
4. Aqueous
59
What does the percentage yield mean?
The efficiency of which reactant are converted into products
60
What are the reasons for not obtaining 100% yield? (5)
- reaction may be at equilibrium
- the reactants may be impure
- side reactions could happen
- reactants or products may be left behind while transferring
- loss of products during separation and purification
61
How is percentage yield calculated?
Percentage yield = actual amount of product / theoretical amount of product x100
mol/mol
62
What does atom economy tell us about?
The proportion of desired products compared will all the products formed in the reaction
63
How to work out atom economy?
Atom economy = rfm of desired products compared will/ sum of rfm of all products x 100
64
Does 100% yield mean 100% atom economy?
No
Even if all the reactants are converted into products, not all products of the reaction will be the required products
65
Which type of reaction has 100% atom economy?
Addition reactions (2 or more reactants are combined to form a product)
66
When an acid is added to water what ion is released into the solution?
H+
Hydrogen ion
67
Define an acid
Proton donor
68
Describe the dissociation of a strong acid
Full dissociation
69
Define base
Proton acceptor
70
Which base is used to treat acid ingestion?
Magnesium hydroxide
71
What are alkalis?
Based that can dissolve in water to form aqueous hydroxide ions
72
What are atmospheric substances
Substances that can act as acids and bases
73
What is formed when an acid reacts with a carbonate?
Salt, CO2 + H2O
74
What is a salt?
Compound form3d when H+ of an ion os replaced by a metal ion or positive ion
75
What is formed when acids react with metal oxide?
Salt and water
76
What is formed when acids react with metal?
Salt + H2
77
Why are products same when a KE reacts with metal oxides or alkali?
Both are bases
78
How are ammonium salts formed?
When acid reacts with aqueous ammonia
79
What are hydrated crystals?
A crystalline structure containing water
80
What does anhydrous crystals mean?
Crystalline form that contains no water
81
What does a dot formula indicate
The amount of water present in a crystalline structure
82
What is the method to carry out a titration?
1. Using a pipettes, measure volume of a solution
2. Add the solution into a conical flask and add indicator into it
3. Add the other solution into a burger and re or the volume
4. Slowly add the solution in the burrito into the conical flask
5. Swirl the mixture continuously until the end point in reached
6. Repeat until concordat results are obtained
83
What is the colour of methyl orange in an acid, base and at end point?
Acid - red
Base - yellow
End point- orange
84
What is an oxidation number?
The number of electron an atom uses to bond with any other atom
85
What is the oxidation number of an uncombined element e,g C,H,O2
0
86
What is the oxidation number of combined oxygen e.g H2O
2
87
What is the oxidation number of oxygen in peroxides?
-1
88
What is the oxidation number of combined hydrogen e.g NH3, H2S
+1
89
What is the oxidation number of combined hydrogen in metal hydrides e.g LiH
-1
90
What is the oxidation number of a simple ion?
Charge on the ion
E.g
Na = +1
Cl = -1
91
What is the oxidation number of combined fluorine e.g NaF, CaF2
-1
92
When an element has more than one stable oxidation number how is it indicated?
Written as a Roman numeral
93
What is the oxidation number of Fe in iron (III) chloride?
+3
94
What are oxyanions?
Negative ions that have an element along with oxygen
95
What is the oxidation number of S in SO4 2-
+6
Oxygen has an oxidation number of -2
4 x -2 =-8-8
-2 -(-8) = +6
96
Define oxidation in terms of electron transfer and oxidation number
Oxidation is
Loss of electrons
An increase in oxidation number
97
Define reduction in terms of electron transfer and oxidation number
Reduction is
Gain if electrons
A decrease in oxidation number
98
What is a redox reaction?
A reaction in which both oxidation and reduction takes place
99
What is the oxidation number of a metal?
0, because it is an uncombined element
100
What does the principal quantum number indicate?
The shell occupied by the electrons
101
What is a shell?
A group of orbitals with the same principal quantum number
102
How many electrons can the 1st shell hold?
2
103
How many electrons can the 2nd shell hold?
8
104
How many electrons can the 3rd shell hold?
18
105
How many electrons can the 4th shell hold?
32
106
What is an orbital?
A region around the nucleus that can hold up to 2 electrons with opposite spins
107
How many electrons can an orbital hold?
2
108
What are the 4 types of orbitals?
s orbital
p orbital
d orbital
f orbital
109
What is the shape of a s-orbital?
Spherical
110
What is the shape of a p-orbital?
Dumb-bell shape
111
How many orbitals are found in a s-sub shell?
1
112
How many electrons can be held in a S sub shell?
2
113
How many orbitals does a P sub shell have?
3
114
How many electrons can be held in a p sub shell
6
115
How many orbitals are present in a d subshell
5
116
How many electrons can be held in a d subshell
10
117
How many orbitals are found in a f subshell
7
118
How many electrons can fill an f subshell?
14
119
When using electrons in box representation what shape is used to represent the electrons
Arrows
120
What letter is used to represent shell number?
n
121
What are the rules by which electrons are arranged in the shell? (5)
Electrons are added one at a time
Lowest available energy level is filled first
Each energy level must be filled before the next one can fill
Each orbital is filled singly before pairing
4s is filled before 3d
122
What does 4s orbital fill before 3d orbital?
4s orbital has a lower energy than 3d before it is filled
123
What is the Lee from configuration of krypton?
1s2
2s2
2s6
3s2
3sp
4s2
3d10
4p6
124
Which electrons are lost when an atom becomes a positive ion?
Electrons in the highest energy levels
125
What are the 3 main types of chemical bonds?
Ionic
Covalent
Metallic
126
Define ionic bonding
The electrostatic attraction between positive and negative ions
127
Give an example of a ionically bonded substance
NaCl
Sodium chloride-salt
128
Define covalent bonding
Electrostatic attraction between a shared pair of electrons and the nuclei
129
Define metallic bonding
Electrostatic attraction between the positive metal ions and the sea of delocalised electrons
130
Electrons in which shell are represented in a dot and cross diagram?
Outer shell
131
Why does giant ionic lattices conduct electricity when liquid not solid?
In a solid state ions are in fixed position and cannot move. When they are in a liquid state the ions are mobile and cannot move freely move and carry charge
132
Do giant ionic lattices have a high or low melting and boiling point?
High melting and boiling point
A large amount of energy is required to overcome the electrostatic bonds
133
In what type of solvents do ionic lattices dissolve?
Polar solvents
E.g water
134
Why are ionic compounds soluble in water?
Water has a polar bond-
hydrogen atoms have a δ+ charge
oxygen atoms have a δ- charge
These charges are able to attract charged ions
135
What is it called when atoms are bonded by a single pair of shared electrons?
A single bond
136
How many covalent bonds does carbon form?
4
137
How many covalent bonds does oxygen form?
2
138
What is a lone pair?
Electrons in the outer shell that are not involved in the bonding
139
What is formed when atoms share 2 pairs of electrons?
A double bond
140
What is formed when atoms share 3 pairs of electrons?
A triple bond
141
What is average bond enthalpy?
Measure of average energy needed to break the bond
142
What is a dative covalent bond?
A bond where both of the shared electrons are supplied by one atom
143
How do Oxonium ions form?
Formed when acid is added to water
H30+
144
What does expansion of the octet mean?
When a bonded atom has more than 8 electrons in the outer shell
145
What are the types of covalent structure?
Simple molecular lattice
Giant covalent lattice
146
Describe the bonding in simple molecular structures
Atoms within the same molecule are held by strong covalent bonds and different molecules are held by weak intermolecular forces
147
Why do simple molecular structures have a low melting and boiling point
Small amount of energy is needed to overcome the intermolecular forces
148
Can simple molecular structures conduct electricity
No, they are non conductors
149
Why do simple molecular structures not conduct electricity?
The have no free charged particles to move around
150
Simple molecular structures dissolve in what type of solvent?
Non polar solvents
151
Give examples of giant covalent structures
Diamond
Graphite
Silicon dioxide SiO2
152
List properties of giant covalent structures (3)
High melting and boiling point
Non conductors of electricity, except graphite
Insoluble in polar and non polar solvents
153
How does graphite conduct electricity?
Delocalised electrons present between the layers are able to move freely carrying the charge
154
Why do giant covalent structures have high melting and boiling point
Strong covalent bonds within the molecules requires a lot of energy to be broken
155
What is the structure of diamond
3D tetrahedral structure of C atoms, with each C atom bonded to 4 others
156
What does the shape of a molecule depend on?
Number of electron pairs in outer shell
Number of these electrons which are bonded and lone pairs
157
Which is the shape and bond angle in a shape with 2 bonded pairs and 0 lone pairs?
Linear
180°
E.g CO2
158
What is the shape and bond angle in a shape with 3 bond pairs and 0 lone pairs?
Trigonal planar
120°
BF3
159
What is the shape and bond angle in a shape with 4 bond pairs and 0 lone pairs?
Tetrahedral
109.5°
CH4
160
What is the shape and bond angle in a shape with 5 bond pairs and 0 lone pairs?
Trigonal bipyramidal
90° and 120°
PF5
161
What is the shape and bond angle in a shape with 6 bonded pairs and 0 lone pairs?
Octahedral
90°
SF6
162
What is the shape and bond angle in a shape with 3 bond pairs and 1 lone pairs?
Pyramidal
107°
NF3
163
What is the shake and bond angle in a shape with 2 bone pairs and 2 lone pairs?
Non linear
104.5°
H20
164
How many degrees does each lone pair reduce the bond angle?
2.5°
165
Define electronegativity
The ability of an atom to attract the pair of electrons in a covalent bond
166
In which direction of the periodic table does electronegativy increase
Top right
Towards fluorine
167
What does it mean when the bond is non polar
The electrons in the bind are evenly distributed
168
What is the most electronegative element?
Fluorine
169
How is a polar bond formed?
Bonding atoms have different electronegativities
170
Why is H2O polar whereas CO2 is non polar?
CO2 is a symmetrical molecule so there is no overall dipole
171
What is meant by intermolecular force?
Attractive force between neighbouring molecules
172
What are the 2 types of intermolecular forces
Hydrogen bonding
Van der Waals’ forces
173
What is the strongest type of intermolecular force
Hydrogen bonding
174
What are the 2 interactions that can be referred as Van der Waals’ forces?
Permanent dipole - induced dipole interaction
Permanent dipole - permanent dipole interaction
175
Describe permanent dipole-induced dipole interactions
When a molecule with a permanent dipole is close to a non polar molecule is causes the non polar molecule to become slightly polar leading to attraction
176
Describe permanent dipole - permanent dipole interactions
Some molecules with polar bonds have permanent dipoles —> forces of attraction between those dipoles and those of neighbouring molecules
177
Describe London forces
London forces are caused by random movements of electrons
This leads to instantaneous dipoles
Instantaneous dipole induces a dipole in nearby molecules
Induced dipoles attract one another
178
Are London forces greater in smaller or larger molecules
Larger molecules due to more electrons
179
Does boiling point increase or decrease down the noble gas group?
Boiling point increases
The number of electrons increases and the strength of London forces also increases so more energy is needed to break bonds
180
What conditions are needed for hydrogen bonding to occur
O-H, N-H or F-H bond
Lone pair of electrons on O, F, N
O,N,F are highly electronegative, H nucleus is left exposed
Strong force of attraction between H nucleus and lone pair of electrons on O,N,F
181
Which is ice less dense than liquid water?
In ice water molecules are arranged in an orderly pattern. It has an open lattice with hydrogen bonds
In water, the lattice is collapsed and the molecules are closer together
182
Why does water have a melting/boiling point higher than expected?
Hydrogen bonds are stronger than other intermolecular forces so extra strength is required to overcome the forces
