Topic 1 - Key Concepts In Chemistry Flashcards
1
Q
What would the word equation be if methane burned in oxygen , giving carbon dioxide and water ?
A
Methane + oxygen —-> carbon dioxide + water
2
Q
What are the molecules on the left hand side of an equation called?
A
The reactants
3
Q
What are the molecules on the right hand side of an equation called?
A
The products
4
Q
What would the symbol equation be if we combined 2Mg+0^2
A
2MgO
5
Q
What does aq ( aqueous) mean?
A
Dissolved in water
6
Q
Chemical formula for…
Water, carbon dioxide , chlorine , ammonia , hydrogen , oxygen
A
Water - H^2O
Carbon dioxide - CO^2
Chlorine - Cl^2
Ammonia - NH^3
Hydrogen - H^2
Oxygen - O^2
7
Q
How do we get an ionic equation and what is it?
A
An ionic equation is the useful bit of a reaction.
We get it by crossing out anything that’s the same on both sides
8
Q
What is a hazard?
A
Something that has the potential to cause harm or damage.
9
Q
What are the different symbols and hazards in chem ?
A
10
Q
The two types of risks accociated with chemistry experiments …
A
1) the equipment
2) the chemicals
11
Q
Ways students could reduce risk?
A
Use a Lowe concentration of the chemical , wear gloves and goggles. Tie hair back
12
Q
Who came up with the plum pudding model and what did it show ?
A
JJ Thomson
It Said an atom was a ball of positive charge with electrons stuck in it
13
Q
Who proved the plum pudding model wrong ?
A
Ernest Rutherford
14
Q
What was ernest Rutherford gold foil experiment?
A
Firing positively charged alpha particles at an extremely thin sheet of gold.
15
Q
What did Ernest Rutherford expect to happen?
A
Rutherford expected the particles to pass straight through and some to be slightly deflected
16
Q
What were Rutherford observations ?
What did he conclude from this?
A
- Rutherford found most particles went straight through the gold, some were deflected more than expected
-From this , Rutherford concluded there was a small posit kt charged nucleus at the centre of an atom. Most of the atom. Is empty space and electrons surround the nucleus
17
Q
What was Niels bohr proposal to the model of the atom?
A
He proposed that electrons sat on shells .
18
Q
What subatomic particles do atoms contain?
A
-protons
-neutrons
-electrons
19
Q
Relative charge and relative mass of a proton
A
Relative Mass =1
Relative charge = +1
20
Q
Relative charge and relative mass of a neutron…
A
Relative charge - 0
Relative mass - 1
21
Q
Relative mass and relative charge of an electron
A
Relative mass =0.0005
Relative charge=-1
22
Q
Where is the nucleus found?
What particles are found r inside it?
What is the nucleuses charge ?
A
-The nucleus is found in the middle of an atom.
- protons and neutrons make up up the nucleus
- nucleus has a positive charge because of tbe protons
23
Q
Where are electrons found?
What are electrons charge ?
Are they bigger or smaller than protons and neutrons ?
A
-Electrons are found on shells orbiting the nucleus
-electrons have a negative charge
- they are smaller than protons and neutrons. Very small mass
24
Q
Why are atoms neutral, unlike ions.
A
Because number of protons = number of neutrons.
25
Why do ions have a charge?
Because the number of protons doesn’t = the number of neutrons
26
What is the mass number?
The mass number is the total number of protons + neutrons in an atom.
27
What’s the atomic number / proton number ?
The number of protons in an atom
28
What is an isotope?
A different form of the same element. Same number of protons and electrons, different number of neutrons
29
Equation for relative atomic mass? ( Ar)
Relative atomic mass = sum of ( isotope abundance X isotope mass) / sum of abundances of all the isotopes
30
Examples of finding relative atomic mass?
31
Who made the first proper periodic table ?
Dimitri Mendeleev
32
What did Mendeleev put the elements in their order based on?
Their atomic mass
33
What is a group in the periodic table?
What are groups based on?
The group is the vertical colum
It’s based on the number of electrons on the outer shell.
34
What are periods in the periodic table?
What are periods based on?
Periods are the horizontal rows
They are based on the number of full electron shells
35
How many electrons are found on each shell
Shell 1 - 2 electrons
Shell 2 - 8 electrons
Shell 3 - 8 electrons
36
If an element is in group 5, how many electrons are there on its outer shell ?
5 electrons
37
Sulfur is in group 6, period 3
Using this information, what is its electronic configuration?
It has 6 electrons on its outer shell. It has 3 shells. This means its configuration must be 2.8.6
38
When do simple ions form?
When an atom gains of looses electrons.
39
Why do atoms loose or gain electrons and become ions?
Because they’re trying to get a full outer shell.
40
When does a negative ion form?
A negative ion ( anion) forms when atoms gain electrons, they have more electrons than protons
41
When does a positive ion form?
A positive ion (cation) forms when an atom looses electrons. Resulting in more protons than electrons
42
What would the charge of an electron be if an atom lost 2 electrons?
2 +
43
What elements form ions easiest ?
Groups 1,2 6,7
44
Where are metals located on the periodic table?
Where are non- metals located?
Metals are located on the left
Non metals are on the right
45
What charge of ion does each group often form?
Group 1 =
Group 2 =
Group 6=
Group7=
Group 1 = 1+ ion
Group 2 = 2+ ion
Group 6 = 2-ion
Group 7= 1 - ion
46
Between what elements does ionic bonding happen?
Between a metal and a nonmetal
47
What happens in ionic bonding?
The metal looses electrons to form a positively charged ion. These electrons are transfered to the non metal to form a negatively charged ion.
The oppositely charged ions are attracted by electrostatic forces
48
What Diagrams do we draw to represent ionic bonds?
Dot and cross diagrams
49
How is sodium chloride formed (ionic bonding)
Sodium is a group 1 metal so it gives up one electron. Making it a positively charged ion. Chlorine picks up one electron as it’s in group7 making it a negatively charged ion.
50
What does a dot and cross diagram look like?
51
What’s the structure of an ionic compound called?
How is an ionic compound held together
Example of an an ionic compound
A giant ionic lattice.
Through strong electrostatic forces between the oppositely charged ions.
Sodium chloride
52
Diagrams that represent a giant ionic lattice …
53
Properties of ionic compounds…
- High melting and boiling point due to strong electrostatic forces of attraction between the ions. Takes lots of energy to overcome this.
- they can’t conduct electricity when solid because the electrons are stuck in place.
- they can conduct electricity when melted because the ions are free to move
54
What is the overall charge of an ionic compound ?
0
55
Advantages of 2d models?
Disadvantages ?
Advantage - good at showing what the atom contains and how’s it’s all connected
Disadvantages- doesn’t show the shape of the atom
56
Advantages and disadvantages of dot and cross diagrams as models.
Advantages - useful for showing how compounds are formed
Disadvantages- don’t show you how the atoms are arranged
57
Advantages and disadvantages of 3 d models such as a ball and stick model.
Advantage - they’re great for visualising a structure
Disadvantage- they don’t show the correct scales of atoms
58
What’s a covalent bond?
A strong bond that forms when a pair of electrons is shared between atoms
59
What type of substances are made of covalent bonds?
Simple molecular substances
60
Diagrams of covalent bonding …
61
What are the electro static forces like in a simple molecular substance made of covalent bonds ?
The electrostatic forces are very weak in simple molecular substance made up of covalent bonds
62
How are the atoms within the molecules held together in simple molecular substances ?
With strong covalent bonds
63
What do you need to do to melt a simple molecular substance ?
You need to break the intermolecular forces NOT the covalent bonds
64
Properties of simple molecular substances …
Example of one
- very low melting and boiling points
- simple molecular substances are liquid or gas at room temp
-they don’t conduct electricity as there’s no free electrons or ions
Hydrogen
65
Properties of giant covalent structures …
Example of one..
- high melting point as all atoms are bonded together by strong covalent bonds. Lots of energy is needed to break these.
-apart from graphite and graphine, they don’t have charged particles so can’t conduct
-they aren’t soluble in water
-diamond
66
How many covalent bonds does carbon form in diamond?
Carbon forms 4 covalent bonds in diamond
67
Why does diamond have a high melting point ?
Because the strong covalent bonds require lots of energy to break.
68
What do the strong covalent bonds in diamond do?
- give it a high melting point
- hold the rigid lattice structure
69
Why doesn’t diamond conduct electricity ?
Diamond doesn’t conduct electricity because it doesn’t have a free ion or electron
70
How many covalent bonds does each carbon atom form in graphite?
Each carbon atom forms 3 covalent bonds in graphite
71
Why is graphite soft and slippery?
Because the covalent bonds between the layers are very weak
72
Why’s graphite got a high melting point ?
Graphite has a high melting point because of strong covalent bonds in the layers need lots of energy to break
73
How does graphite conduct electricity ?
Graphite conducts electricity because only 3 out of its 4 outer electrons are used in bonding. This means it has a delocalised electron to carry the charge.
74
What is graphene?
Graphene is one layer of graphite
Carbon atoms joined in hexagons
75
What are fullerenes made of?
What shapes do fullerenes form?
Fullerenes are made of carbon
Fullerenes are shaped like closed tubes or hollow balls
76
What do fullerenes do and why?
Fullerenes “cage “ other molecules. This can be used to engulf a molecule and deliver it directly to cells in the body.
77
Why do fullerenes have a large surface area?
Fullerenes have a large surface area so they make great industrial catalysts
78
2 types of fullerenes
-Nanotubes
-buckminsterfullerene
79
Properties of nanotubes as a fullerene…
-Made of graphite cylinders so they conduct electricity
- have high tensile strength so they can be used to strengthen materials without adding much weight. Eg: sports equipment:
80
What’s buckminster made of?
20 hexagons and 12 pentagons
81
What are polymers made up of ?
Polymers are made up of covalently bonded carbon atoms
Formed when monomers join together
82
What is the structure of metals ?
Metals have a giant structure
83
What is the structure of metals ?
Metals have a giant structure
84
How does metallic bonding work?
metallic bond is the force of attraction between these free-moving (delocalised) electrons and positive metal ions. Metallic bonds are strong
85
Physical properties of metals and why?
-metals have high melting and boiling points as there are strong electrostatic forces between the sea of delocalised electrons and the positive ions. These require lots of energy to break
-metals are more dense than non metals, because the ions are packed closer together.
-metals are malleable because the layers can slide over eachover
-they are good conductors of electricity because of the delocalised electrons that carry a charge.
86
Is mass always conserved in a chemical reaction?
Mass is always conserved in a chemical reaction.
87
What must it mean if there’s a change in Mass in a chemical reaction?
There must be a gas involved
88
What does it mean if the mass increases within a chemical reaction?
If the mass increases, it means the oxygen or gas has been reacted with the reactants such as a metal and combined with it
89
What does it mean if the mass decreases in a chemical reaction but the reactants haven’t gone?
The gas has escaped
90
What is relative formula mass?
The relative formula mass (Mr) is all the relative masses of a compound added together.
91
What’s the empirical formula?
The empirical formula of a compound is the simplest ratio of atoms.
92
What would the empirical formula of C6H12O6 be
CH2O
93
How do you get the molecular formula ?
-You find the Mr of the empirical formula.
-then do Mr of the compound / Mr of the empirical formula.
-then multiply everything in the empirical formula by the result above.
94
What is a mole?
What is avagrados number?
What does avagrados number help us do?
The relative mass of a substance in grams.
6.02 X 10^23
Find the number of particles in 1 mol of a substance
95
Equation for the number of moles…
Number of moles = Mass (g)/Mr
96
Formula triangle for moles mass and mr
97
What is the solute?
The solid your dissolving
98
What is the unit for concentration?
g dm^-3
99
Equation for concentration?
Concentration = mass of solute/ volume of solution
100
1dm^3 = …cm^3
1dm^3 = 1000cm^3
101
How would you find the empirical formula of a sample by using masses?
You would find the moles by doing Moles = mass/ Rm.
Put the moles of the elements in a ratio. Then divide the ratio by the smaller number to find the empirical formula using mass. For example, if the ratio ended up being C:H. 1:2. The empirical formula would be CH2
102
Practical to calculate empirical formula …
1)clean a crucible then weigh it along with its lid.
2)add magnesium ribbon to the crucible. Weigh the crucible lid , the crucible with the magnesium in it. The weight of the magnesium will be the overall - crucible and lid.
3) heat the crucible, leave a gap in the lid to let oxygen enter.
4)heat until magnesium ribbon has turned white
5) reweigh all of this, and find the mass of the magnesium oxide.
103
What is the limiting reactant ?
The reactant that is used up first in a reaction, limits the amount of product produced. Fully used up
104
What’s the reactant that isn’t used up called in a Chemical reaction?
The excess.
105
How to calculate the amount of product from a limiting reactant?
1)write out a balanced equation
2)work out relative formula masses of the reactant and the product your interested in.
3)find how many moles there are of the substances you know the mass off
4)used the balances equation to find out how many moles there will be of the other substance.
5)use the number of moles to calculate the mass.
106
How can you work out the limiting reactant of a reaction?
1)Divide the mass of each substance by its Mr. To find out how many moles of each substance were reacted.
2)divide by the smallest number of moles.
3)compare the ratio between The moles of the products and the balanced equations.
107
How do you calculate % mass?
% Mass = Ar X 100/ Mr
108
Moles and concentration triangle?
109
Moles and concentration triangle?
110
Moles and volume triangle
111
If the molecular formula of something is C2H6 what is the impirical formula ?
CH3
112
If the molecular formula of something is C2H6 what is the impirical formula ?
CH3
