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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
Q

How to find formula of compound with the reactants

A

Calculate moles of each reactant and divide both by the smaller answer
Find ratio and then put it together into an equation

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26
Q

How to find formula of reactant from the products

A

Calculate moles of the elements in the reactant
Divide by smallest and find ratio and put into equation

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27
Q

How to find formula of reactant through the weights of multiple products

A

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

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28
Q

What is a relative mass

A

It is a comparative value which is a mass compared to some standard mass

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29
Q

What is relative atomic mass, Ar

A

It is the average mass of an atom of an element on a scale where an atom of carbon-12 is exactly 12

30
Q

Equation for relative atomic mass

A

(% x mass) / 100

31
Q

What is relative molecular mass, Mr

A

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
Q

What is relative formula mass, Mr

A

It is the average mass of a formula unit on the scale where an atom of carbon 12 is exactly 12

33
Q

Equation for relative molecular and formula masses

A

(number of atoms x mass)

34
Q

What is a mole

A

A mole of a substance is 6.02 x1023 particles of it

35
Q

What is avogadros number

A

6.02 x10 23

36
Q

What is one mole of a substance

A

One mole of a substance is its Ar or Mr in grams

37
Q

Why do we need moles

A

Because when we talk about equal amounts in chemistry we mean equal numbers of particles and not equal masses

38
Q

Equation for number of moles

A

moles = mass / Mr

39
Q

What is the equation for number of particles

A

No of particles = moles x Avogadro’s number

40
Q

What is a reading

A

A reading is a value found from a single judgement when using a piece of equipment

41
Q

What is the uncertainty in a reading

A

It is at least + - 1/2 of the smallest division on the equipment

42
Q

What is a measurement

A

It is a value found from the difference between the judgements of two readings

43
Q

What is the uncertainty in a measurement

A

It is at least + - 1 of the smallest division on the equipment

44
Q

What is the equation for % uncertainty

A

overall uncertainty/value x100

45
Q

How do you construct an ionic equation

A

Split up the compounds into ions if substance is a liquid in aqueous state
Remove spectator ions

46
Q

What salts and hydroxides are soluble

A 
All sodium, potassium and ammonium salts
All nitrates
Most chlorides, bromides and iodides
Most sulphates
Sodium, potassium and ammonium hydroxides
47
Q

What salts and hydroxides are insoluble

A 
Silver and lead chlorides, bromides and iodides
Lead and barium sulphate
Calcium sulphate is sparingly soluble
Most other carbonates
Most other hydroxides
48
Q

What is a soluble salt

A

It is one which will dissolve in water at room temperature

49
Q

What is an insoluble salt

A

It is one which will not dissolve in water at room temperature

50
Q

What is a sparingly soluble salt

A

It is one which will dissolve slightly in water

51
Q

What do chemical equations refer to quantity in

A

moles

52
Q

What is a tonne converted into kg and g

A

1000 kg
1,000,000 g

53
Q

What does it mean when a substance is in excess

A

It is when more of a substance is used than needed so not all of it will react

54
Q

What is the limiting reagent

A

The reactant that is not in excess

55
Q

What is the equation for percentage yield

A

actual yield/theoretical yield x100

56
Q

What does percentage yield measure

A

The efficiency of the chemical process

57
Q

What is the equation for atom economy

A

Total Mr of desired product/Total Mr of reactants (or products) x100

58
Q

What does atom economy measure

A

What proportion of the products of a reaction are the desired product and how much is waste

59
Q

What does the volume of a gas depend on

A

The temperature
The pressure
number of moles of it

60
Q

Under the same conditions what will 1 mole of two gases share

A

the same volume

61
Q

What id the ideal gas law equation

A 
PV = nRT
Pressure in Pa
Volume in m3
Number of moles
Gas constant 8.31 J/K/mol
Temperature in Kelvin - degrees + 273
62
Q

What is the conversion from cm3 to m3 and dm3 to m3

A

x10-6
x10-3

63
Q

What does the concentration of a solution tell us

A

How much solute is dissolved in a known volume of solution

64
Q

How do you convert from mol/dm3 to g/dm3

A

multiply by the Mr

65
Q

What is the equation for concentration

A

moles/ volume (dm3)
moles x1000/volume (cm3)

66
Q

What is a titration

A

It is a procedure where a solution of known concentration is used to determine an unknown concentration

67
Q

What is the percentage error of a pipette

A

0.05/25 x100 = 0.2%

68
Q

What is the percentage error of a burrette

A

0.15/average titre x100

69
Q

What is the percentage error of a 1 and 2 decimal point weigher

A

0.1/mass weighed x 100
0. 01/mass weighed x 100

70
Q

What is the percentage error of a volumetric flask

A

0.5/250 x 100 = 0.2%

71
Q

What is a back titration

A

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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