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Chemistry A Level > Amount of Substance - Chapter 2 > Flashcards

Amount of Substance - Chapter 2 Flashcards

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1
Q

What is the valency of an atom in a molecule

A

The valency in a molecule can be taken as the number of bonds which that atom forms in the compound

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2
Q

What is the valency of an ion

A

The valency of an ion in an ionic compound is equal to the charge on the ion

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3
Q

For metals
Valency =

A

valency = group number

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4
Q

For Non-metals

Valency =

A

Valency = (8-group number)

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5
Q

Formula of Ammonium

A

NH4 +

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6
Q

Formula of Hydrogencarbonate

A

HCO3 -

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7
Q

Formula of Hydroxide

A

OH -

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8
Q

Formula of Phosphate

A

PO4 3-

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9
Q

Formula of Carbonate

A

CO3 2-

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10
Q

Formula of Hydrogensulphate

A

HSO4 -

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11
Q

Formula of Nitrate

A

NO3 -

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12
Q

Formula of Sulphate

A

SO4 2-

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13
Q

What is a chemical equation

A

It is an equation that tells us what is happening in a reaction

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14
Q

What are word equations

A

They are qualitative
May include state symbols
e.g. hydrogen + fluorine -> hydrogen fluoride

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15
Q

What are balanced symbol equations

A 
They are quantitative
Obey the law of conservation of mass
Tell us the number of moles of each substance involved
May include symbol equations
e.g. H2 + F2 -> 2HF
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16
Q

What are balanced symbol equations sometimes called

A

Stoichiometric equations

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17
Q

What elements exist as diatomic molecules

A 
Hydrogen
Oxygen
Nitrogen
Fluorine
Chlorine
Bromine
Iodine
Astatine
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18
Q

What is the equation for % of substance in a compound

A

Mr of substance/Mr of whole compound x100

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19
Q

What is the chemical formula of a compound

A

It is a representation of the composition of a compound

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20
Q

What are the 2 types of formula

A

Empirical formula
Molecular formula

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21
Q

What is the empirical formula

A

The simplest ratio of atoms of each element in a compound

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22
Q

What is the molecular formula

A

The actual numbers of atoms of each element in a molecule

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23
Q

Can ionic compounds have molecular formulas

A

No and they dont apply

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24
Q

How do you convert empirical formula to molecular formula

A

Take the Mr of empirical formula and divide it by the Mr of the molecule and times each atom by that number.

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25
How to find formula of compound with the reactants
Calculate moles of each reactant and divide both by the smaller answer Find ratio and then put it together into an equation
26
How to find formula of reactant from the products
Calculate moles of the elements in the reactant Divide by smallest and find ratio and put into equation
27
How to find formula of reactant through the weights of multiple products
Find moles of elements in the reactant and then the weights Use weights to find the unknown weight of third element Calculate moles and find ratio Put it into a formula
28
What is a relative mass
It is a comparative value which is a mass compared to some standard mass
29
What is relative atomic mass, Ar
It is the average mass of an atom of an element on a scale where an atom of carbon-12 is exactly 12
30
Equation for relative atomic mass
(% x mass) / 100
31
What is relative molecular mass, Mr
It is the average mass of a molecule of an element or compound on a scale where an atom of carbon 12 is exactly 12
32
What is relative formula mass, Mr
It is the average mass of a formula unit on the scale where an atom of carbon 12 is exactly 12
33
Equation for relative molecular and formula masses
(number of atoms x mass)
34
What is a mole
A mole of a substance is 6.02 x1023 particles of it
35
What is avogadros number
6.02 x10 23
36
What is one mole of a substance
One mole of a substance is its Ar or Mr in grams
37
Why do we need moles
Because when we talk about equal amounts in chemistry we mean equal numbers of particles and not equal masses
38
Equation for number of moles
moles = mass / Mr
39
What is the equation for number of particles
No of particles = moles x Avogadro's number
40
What is a reading
A reading is a value found from a single judgement when using a piece of equipment
41
What is the uncertainty in a reading
It is at least + - 1/2 of the smallest division on the equipment
42
What is a measurement
It is a value found from the difference between the judgements of two readings
43
What is the uncertainty in a measurement
It is at least + - 1 of the smallest division on the equipment
44
What is the equation for % uncertainty
overall uncertainty/value x100
45
How do you construct an ionic equation
Split up the compounds into ions if substance is a liquid in aqueous state Remove spectator ions
46
What salts and hydroxides are soluble
``` All sodium, potassium and ammonium salts All nitrates Most chlorides, bromides and iodides Most sulphates Sodium, potassium and ammonium hydroxides ```
47
What salts and hydroxides are insoluble
``` Silver and lead chlorides, bromides and iodides Lead and barium sulphate Calcium sulphate is sparingly soluble Most other carbonates Most other hydroxides ```
48
What is a soluble salt
It is one which will dissolve in water at room temperature
49
What is an insoluble salt
It is one which will not dissolve in water at room temperature
50
What is a sparingly soluble salt
It is one which will dissolve slightly in water
51
What do chemical equations refer to quantity in
moles
52
What is a tonne converted into kg and g
1000 kg 1,000,000 g
53
What does it mean when a substance is in excess
It is when more of a substance is used than needed so not all of it will react
54
What is the limiting reagent
The reactant that is not in excess
55
What is the equation for percentage yield
actual yield/theoretical yield x100
56
What does percentage yield measure
The efficiency of the chemical process
57
What is the equation for atom economy
Total Mr of desired product/Total Mr of reactants (or products) x100
58
What does atom economy measure
What proportion of the products of a reaction are the desired product and how much is waste
59
What does the volume of a gas depend on
The temperature The pressure number of moles of it
60
Under the same conditions what will 1 mole of two gases share
the same volume
61
What id the ideal gas law equation
``` PV = nRT Pressure in Pa Volume in m3 Number of moles Gas constant 8.31 J/K/mol Temperature in Kelvin - degrees + 273 ```
62
What is the conversion from cm3 to m3 and dm3 to m3
x10-6 x10-3
63
What does the concentration of a solution tell us
How much solute is dissolved in a known volume of solution
64
How do you convert from mol/dm3 to g/dm3
multiply by the Mr
65
What is the equation for concentration
moles/ volume (dm3) moles x1000/volume (cm3)
66
What is a titration
It is a procedure where a solution of known concentration is used to determine an unknown concentration
67
What is the percentage error of a pipette
0.05/25 x100 = 0.2%
68
What is the percentage error of a burrette
0.15/average titre x100
69
What is the percentage error of a 1 and 2 decimal point weigher
0.1/mass weighed x 100 0. 01/mass weighed x 100
70
What is the percentage error of a volumetric flask
0.5/250 x 100 = 0.2%
71
What is a back titration
It is a procedure which involves reacting a known mass of an insoluble solid with a known excess of an acid or alkali so that some will be left over

Chemistry A Level (20 decks)

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