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A Level - Chemistry > 5: Formulae > Flashcards

5: Formulae Flashcards

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1
Q

How many particles are in a mole?

A

6.02 x10^23

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2
Q

What is the symbol for moles?

A

n

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3
Q

What is the name of the constant for the number of particles in a mole?

A

Avogadro’s constant, L

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4
Q

What is the equation for moles using just number of atoms?

A

Moles = Number of particles / number of particles in a mole

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5
Q

What is molar mass, M?

A

Mass per mole

Same as the relative atomic mass (Mr)

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6
Q

What is the moles equation?

A

Moles = Mass / molar mass

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7
Q

How would you calculate the number of atoms in something?

A

Number of atoms = Moles x Avogadros constant

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8
Q

What is concentration?

A

The number of moles dissolved in 1 dm3

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9
Q

What is 1 dm3 equivalent to?

A

1 litre

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10
Q

What is the concentration equation for moles?

A

Moles = Concentration x Volume

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11
Q

What is the concentration equation for mass?

A

Mass = Concentration x Volume

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12
Q

What is the unit for concentration?

A

Mol dm-3

or g dm-3

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13
Q

What is empirical formula?

A

Smallest whole number ratio of atoms in a compound

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14
Q

How do you work out the empirical formula from experiment data?

A

Work out how many moles of each product
Divide by the smallest
Ratio must be whole, and is number of atoms in empirical formula

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15
Q

How would you work out empirical formula from percentages?

A

Work out moles as if there is 100g of product and do the same

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16
Q

What is the equation for percentage composition?

A

Percentage composition of X = mass of element in compound / total mass of compound x 100

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17
Q

What is shown in ionic equations?

A

Reacting particles and what is formed

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18
Q

How do you determine what to include in ionic equations?

A

Write out all ions on both sides

Cancel any ions that occur on both sides

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19
Q

What is a spectator ion?

A

An ion that is in the reaction but is not changed

20
Q

What is reaction stoichiometry?

A

Ratios of reactants and products

number before

21
Q

What are the 4 state symbols?

A 
s = solid
l = liquid
g = gas
aq = aqueous (solution in water)
22
Q

What occurs in displacement reactions?

A

More reactive element reacts to take the place of less reactive element

23
Q

What occurs when an acid reacts with a base?

A

Acid + Base -> Salt + Water

2H+ + 2OH- -> 2H2O

24
Q

What occurs when an acid reacts with a carbonate?

A

Acid + CO3- -> Salt + Water + CO2

2H+ + CO3 2- -> H2O + CO2

25
Q

What is the volume equation?

A

Moles = Volume in dm3 / molar gas volume

26
Q

What is the molar gas volume at room temp. & pressure?

A

24 dm3 mol-1

27
Q

What is the molar gas volume at standard temp. & pressure?

A

22.4 dm3 mol-1

28
Q

How can you find the volume of a gas?

A

Collecting gas in a gas syringe

Displacing water from measuring cylinder

29
Q

What is the ideal gas equation?

A 
pV = nRT
p = pressure (Pa)
V = volume (m3)
n = moles
R = 8.31 J K-1 mol-1
T = Temperature (K)
30
Q

How do you convert degrees Celsius to kelvin?

A

K = C + 273

31
Q

What is the gas constant?

A

R = 8.31 J K-1 mol-1

32
Q

How do you convert cm3 to m3?

A

m3 = cm3 x 1/1000000

33
Q

How do you convert dm3 to m3?

A

m3 = dm3 x 1/1000

34
Q

How would you use the ideal gas equation to work out the molar mass of an unknown, volatile liquid?

A 
Put a known mass of liquid in flask
Attach sealed gas syringe
Warm until fully evaporated
Record volume of gas and temp.
Use equation to work out how many moles and then molar mass
35
Q

What is a hazard?

A

Anything that has potential to cause harm or damage

36
Q

What is a risk?

A

Probability of someone being harmed

37
Q

What is a standard solution?

A

A solution that has a known concentration

38
Q

What is the function of a burette?

A

Measure different volumes and let you add solution drop by drop

39
Q

What is the function of a pipette?

A

Measure only one volume of solution

40
Q

How do you use a pipette?

A

Fill the pipette to just above the line and take out of solution and drop to line for exact measurement

41
Q

Give the steps to do a titration

A

Measure alkali of unknown conc. using a pipette
Add a few drops of an indicator such as phenolpthalein
Rinse & fill a burette with the standard solution
Perform rough titration to estimate end point until permanent change
Perform accurate titration until 2 cm3 of end point then add acid by drop
Work out acid to neutralise acid, the titre
Repeat until titres are concordant (within 0.1 cm3 of eachother)

42
Q

What are the two main indicators for acid/alkali reactions?

A

Methyl orange - yellow to red when adding acid to alkali

Phenolphthalein - red to colourless when adding acid to alkali

43
Q

How can you obtain g dm-3 from the mol dm-3?

A

g dm-3 = mol dm-3 x Mr

44
Q

What is the calculation for volume?

A

volume (cm3) = moles x 1000 / concentration

45
Q

What are the assumptions of an ideal gas?

A

There are no (or negligible) intermolecular forces between the gas molecules
The volume occupied by the molecules is negligible relative to the volume of the container
Temp is proportional to average kinetic energy of molecules
All collisions are perfectly elastic (no loss of kinetic energy)
Pressure is due to collisions between molecules and wall of the container
Molecules behave as rigid spheres

46
Q

Which gases behave like ideal gases?

A

Those which are well above their boiling points

Nitrogen, oxygen, hydrogen and noble gases

47
Q

How do you convert different volumes?

A

1 m3 = 1000 dm3 = 1000000 cm3

A Level - Chemistry (26 decks)

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