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Chemistry Formulas and Key concepts > 2.1 - Key concepts > Flashcards

2.1 - Key concepts Flashcards

1
Q

Who developed the idea of an atom by pounding up materials in his pestle and mortar until he had reduced them to smaller particles?

A

Democritus (460 BC)

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2
Q

Who suggested that all matter was made up of tiny spheres that were able to bounce around with perfect elasticity?

A

John Dalton (1808)

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3
Q

Who found that atoms could sometimes eject a far smaller negative particles which was called an electron?

A

Joseph John Thomson (JJT) - 1898

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4
Q

Who developed the idea that an atom was made up of electrons scattered unevenly within an elastic sphere surrounded by a soup of positive charge to balance the electrons charge?

A

Joseph John Thomson (JJT) - 1904

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5
Q

What did Geiger and Marsden do, and what did they find? (1910)

A

Ernest Rutherford, oversaw Geiger and Marsden (1910)
They fired HELIUM nuclei at a piece of gold foil which was only a few atoms thick
They found that although MOST of them passed through, a small number where deflected

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6
Q

What did this new evidence allow rutherford to do?

A

This evidence allowed him to propose a more detailed model with a central nucleus. He suggested that the positive charge was all in a central nucleus. With this holding the electrons in place by electrical attraction

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7
Q

What did Niels Bohr say about Rutherford’s model?

A

He believed that it was a great model BUT he added in by stating that the electrons were in orbitals

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8
Q

What is the relative mass and relative charge of a proton?

A

Relative charge - +1

Relative mass - 1

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9
Q

What is the relative mass and relative charge of a neutron?

A

Relative charge = 0

Relative mass = 1

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10
Q

What is the relative mass and relative charge of a electron?

A

Relative charge = -1

Relative mass = 1/2000

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11
Q

What is an isotope?

A

An isotope is an atom of the same element but with different numbers of NEUTRONS and different masses

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12
Q

What is meant by relative isotopic mass

A

Mass of an isotope compared with 1/12th mass of carbon-12

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13
Q

Define relative atomic mass

A

Weighted mean mass of an atom compared with 1/12th mass of carbon-12

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14
Q

In an element, what will NEVER change

A

Proton number

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15
Q

What is an ion?

A

An element that has an imbalance of protons and electrons (charged particle)

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16
Q

Describe the reaction of isotopes

A

Chemical reactions of isotopes will be the same as all the forms of that isotope because chemical reactions ONLY involve electrons. Therefore, different isotopes of the same elements, react in the SAME way.

NOTE: The number of neutrons makes NO difference to chemical reactivity.

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17
Q

How can you find the atomic mass of an element

A

Multiply EACH isotopic mass by its percentage abundance, add the results together and then divide by the sum of the percentages

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18
Q

What is mass spectrometry used for?

A

Mass spectrometry is used to:

  • Identify an unknown compound
  • Find the relative abundance of each isotope of an object
  • Determine structural information about molecules
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19
Q

How can we interpret the mass spectrum?

A
  • Positions of the peaks gives the atomic mass
  • Peak intensity gives you relative abundance
  • Highest peak is scaled to 100% and the other values are adjusted accordingly
  • m/z on the x axis
  • % abundance on the y axis
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20
Q

How do you work out relative formula mass?

A

Adding all the relative ATOMIC masses together

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21
Q

Define Ionic bonding

A

Ionic bonding is electrostatic attraction between positively and negatively charged ions

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22
Q

What are the 5 ionic elements required on your specification?

A 
Hydroxide ion = OH-
Nitric acid ion = NO3-
Carbonate ion = CO3 (2- ion
)Sulphate ion - SO4(2-)
Zinc ion = Zn+
Silver ion = Ag+
Ammonium ion - NH4+
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23
Q

What is the general equation for positive ions in each group

A

Group 1 - M+
Group 2 - M(2+)
Group 3 - M(3+)

Where M = A metal
2+ = 2+ ion
3+ = 3+ ion

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24
Q

What is the general equation for negative ions in each group

A

Group 7 = N-
Group 6 = N(2-)
Group 5 = N(3-)

Where N = A non- metal
2- = 2- ion
3- = 3- ion

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25
What are the state symbols?
(s) = Solid (l) = Liquid (g) = Gas otherwise known as gaseous (aq) = aqueous
26
Define empirical formula
The simplest whole number ratio of elements in a compound
27
How do you calculate the empirical formula (from grams composition)?
1) Divide each amount (of grams) by its atomic mass) 2) Divide each of these answers by whichever answer is the smallest 3) Find the lowest WHOLE NUMBER ratio
28
How do you calculate the empirical formula (from percentage composition)?
1) Divide each percentage by its atomic mass) 2) Divide each of these answers by whichever answer is the smallest 3) Find the lowest WHOLE NUMBER ratio
29
What is meant by amount of substance?
The quantity chemists use to count atoms
30
What is the mole
The unit for amount of substance
31
What is Avogadro's constant?
The number of particles per mole
32
What is molar mass?
Mass per unit mole
33
What is the formula for amount of substance(moles)
n = mass DIVIDED by Mr
34
Define molecular formula
The number and type of atoms of each element in a molecule
35
How do you calculate molecular formula?
You work out the Mr of the empirical formula and divide it by the area of the desired product. You then times this answer by the number of atoms of each elements
36
How much volume does 1 mole of any gas occupy at RTP?
24.0 dm^3
37
How much volume does 2 moles of any gas occupy at RTP?
48.0 dm^3 NOTE: Goes up in 24's
38
Define molecular formula
The number and type of atoms of each element in a molecule
39
How do you calculate molecular formula?
You work out the Mr of the empirical formula and divide it by the area of the desired product. You then times this answer by the number of atoms of each elements
40
What is the gas volume equation?
V(dm^3) = n x 24 V (cm^3) = n x 24000 NOTE: This formula is used when working out gas volume at RTP(Room temperature and pressure)
41
Will gas volume change with different elements which have different masses?
No it won't. Although these gases have different masses, these differences in the individual particles have NO effect on the overall volume between the particles are so SPREAD out that any differences become UNIMPORTANT
42
What is the ideal gas equation?
pV=nRT ``` Where p = pressure V = Volume n = Number of moles R = Gas constant (given on the data sheet - 8.314) T = Temperature ```
43
1
1
44
What is the ideal gas equation?
pV=nRT ``` Where p = pressure (Pa) V = Volume (m^3) n = Number of moles (mol) R = Gas constant (given on the data sheet - 8.314) T = Temperature (Kelvins) ``` NOTE: Don't get confused between celsius and Kelvin,. To get from Celsius to Kelvin add 273 To get from Kelvin to Celsius, minus 273
45
How do you calculate molecular formula?
You work out the Mr of the empirical formula and divide it by the area of the desired product. You then times this answer by the number of atoms of each elements
46
Define water of crystallisation
Water molecules that form an essential part of the crystalline structure of a compound
47
What is a hydrated compound?
A compound with water in it's crystalline structure
48
How do you work out the dot formula? (steps)
1) Work out the anhydrous mass 2) Calculate the amount, in mol, of anhydrous salt 3) Calculate the mass of water 4) Calculate the amount,in mol, of water 5) Determine the formula of the hydrate salt using the molar value. (divide by smaller number )
49
Define percentage yield
The percentage yield of a reaction measures the reaction's efficiency.
50
Define theoretical yield
The amount of product that could possibly be produced in a given reaction
51
Define actual yield
The amount of product TRULY obtained in a chemical reaction
52
What is the formula for percentage yield?
[Actual yield (in moles)] / [Theoretical yield (in moles)] x 100
53
Why will percentage yield never by at 100%?
- The reaction may be at equilibrium and may not reach completion - Side reactions may occur, leading to by-products - The reactants may not be pure. Therefore, you can't get 100% actual yield - Some of the reactants or products may be left behind in some equipment used in the experiment - Separation and purification may result in the loss of some products
54
Define atom economy
The amount of starting materials, that end up as useful products
55
How do you work out the atom economy?
1) Identify the useful product 2) Work out the Mr of all the products 3) Use the formula to calculate the atom economy
56
If a reaction only has one product, what is its atom economy?
100%
57
If a reaction has more than product, what is its atom economy?
LESS THAN 100%
58
What are the benefits of a high atom economy?
Conservation of resources and creating less waste
59
What is a solution dissolved in water also known as?
An aqueous solution
60
Define an acid
A proton donor
61
Define an alkali
A water soluble proton acceptor
62
Define a base
A proton acceptor
63
Recall all of the common acids
Hydrochloric acid - HCl Nitric acid - HNO3 Sulfuric acid - H2SO4 Ethanoic acid - CH3COOH
64
Recall all of the common alkalis
Sodium hydroxide - NaOH Potassium hydroxide - KOH Ammonia - NH3
65
In aqueous solutions, what do STRONG acids do?
Strong acids completely dissociate (split up) into ions e.g. HCl (aq) → H+ (aq) + Cl- (aq) HNO3(aq) → H+ (aq) + NO3- (aq) H2SO4 (aq) → 2H+ + SO4(2-) (aq)
66
In aqueous solutions, what do WEAK acids do?
Weak acids only partially dissociate and are excellent at accepting back the H+ ion e.g. CH3COOH (aq) → CH3COO- + H+ (aq)
67
In aqueous solutions, what do STRONG acids do?
Strong acids completely dissociate (split up) into ions e.g. HCl (aq) → H+ (aq) + Cl- (aq) HNO3(aq) → H+ (aq) + NO3- (aq) H2SO4 (aq) → 2H+ + SO4(2-) (aq)
68
What is meant by a diprotic acid?
An acid capable of donating two protons or hydrogen ions when dissolving in aqueous solutions. e.g. H2SO4 (aq) → 2H+ + SO4(2-) (aq)
69
In aqueous solutions, what do WEAK acids do?
Weak acids only partially dissociate and are excellent at accepting back the H+ ion e.g. CH3COOH (aq) → CH3COO- + H+ (aq)
70
General types of bases?
These include metal oxides , metal hydroxides and ammonia
71
In aqueous solutions, what do STRONG alkalis do?
Strong alkalis completely dissociate into ions in aqueous solution
72
In aqueous solutions, what do weak alkalis do?
Weak bases partially dissociate into ions in aq solution
73
When a weak bases reacts with water what happens?
Weak bases partially react with water to give ions in aqueous solution e.g. Ammonia, NH3
74
The weaker the base, the less it ......................
Dissociates. Therefore, the more, the equilibrium lies to the LEFT
75
NH3+ HCl →
NH4Cl
76
NH3 + H+ →
NH4
77
What is a neutralisation reaction and what happens?
A neutralisation reaction is a reaction where an aqueous acid and an aqueous alkali react to form water. The hydroxide ions (OH-) from the alkali reacts with the hydrogen ions (H+) from the acid to form water
78
Show the neutralisation reaction equation
H+(aq) + OH-(aq) → H20 (l)
79
What is an amphoteric substance
A substance that has the ability to act either as an ACID or a BASE
80
Provide an example of an amphoteric substance
Water, amino acid
81
Why are these amphoteric substances?
They contain both contain a hydroxide ion, which can accept a proton and a hydrogen ion which can donate a proton
82
Acid + metal →
Salt and hydrogen
83
Acid + Metal oxide →
Salt and water
84
Acid + Metal hydroxide →
Salt and water
85
Acid + Metal carbonate →
Salt, water and carbon dioxide
86
In a reaction, how can we tell if an acid is present?
If a hydrogen ion gets replaced by a metal ion
87
What is a titration?
The process of analysing composition by measuring the volume of one solution needed to completely react with another solution
88
What is an analyte?
A solution of unknown concentration
89
What is a Titrant?
A solution of known concentration
90
What is an indicator?
A substance that changes colour when an excess titrant had been added. It identified the end point in a titration experiment e.g. Universal indicator
91
When approached by a titration question, what must you do?
Write everything you know clearly and use the values your given, the formula but most IMPORTANTLY, use the mole ratio!
92
What is the oxidation state of any element in GROUP 1?
+1
93
What is the oxidation state of any element in GROUP 2
+2
94
What is the oxidation state of any element in GROUP 3
+3
95
What is the oxidation number of any element in GROUP 1?
+1
96
What is the oxidation number of any element in GROUP 2
+2
97
What is the oxidation number of any element in GROUP 3
+3
98
What is the oxidation number of any element in GROUP 5
-3
99
What is the oxidation number of any element in GROUP 6
-2
100
What is the oxidation number of any element in GROUP 7
-1
101
What is the oxidation number of an element?
0
102
What does the oxidation number of a compound add up to? (unless it's ionic)
0
103
What is the oxidation number of an ionic compound?
It's ionic charge
104
What will ALWAYS be the oxidation number of fluorine?
-1
105
What is the oxidation number of hydrogen?
+1 EXCEPT in metal hydrides where it is -1
106
What is the oxidation number for oxygen?
-2 EXCEPT in F20 and peroxides
107
What is the oxidation number for chlorine?
-1 EXCEPT when bonded to oxygen

Chemistry Formulas and Key concepts (8 decks)

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