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A Level - Chemistry > 5: Formulae > Flashcards

5: Formulae Flashcards

(47 cards)

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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?

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A

An ion that is in the reaction but is not changed

20
Q

What is reaction stoichiometry?

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A

Ratios of reactants and products

number before

21
Q

What are the 4 state symbols?

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

What occurs in displacement reactions?

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A

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

23
Q

What occurs when an acid reacts with a base?

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A

Acid + Base -> Salt + Water

2H+ + 2OH- -> 2H2O

24
Q

What occurs when an acid reacts with a carbonate?

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A

Acid + CO3- -> Salt + Water + CO2

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

25
What is the volume equation?
Moles = Volume in dm3 / molar gas volume
26
What is the molar gas volume at room temp. & pressure?
24 dm3 mol-1
27
What is the molar gas volume at standard temp. & pressure?
22.4 dm3 mol-1
28
How can you find the volume of a gas?
Collecting gas in a gas syringe | Displacing water from measuring cylinder
29
What is the ideal gas equation?
``` pV = nRT p = pressure (Pa) V = volume (m3) n = moles R = 8.31 J K-1 mol-1 T = Temperature (K) ```
30
How do you convert degrees Celsius to kelvin?
K = C + 273
31
What is the gas constant?
R = 8.31 J K-1 mol-1
32
How do you convert cm3 to m3?
m3 = cm3 x 1/1000000
33
How do you convert dm3 to m3?
m3 = dm3 x 1/1000
34
How would you use the ideal gas equation to work out the molar mass of an unknown, volatile liquid?
``` 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
What is a hazard?
Anything that has potential to cause harm or damage
36
What is a risk?
Probability of someone being harmed
37
What is a standard solution?
A solution that has a known concentration
38
What is the function of a burette?
Measure different volumes and let you add solution drop by drop
39
What is the function of a pipette?
Measure only one volume of solution
40
How do you use a pipette?
Fill the pipette to just above the line and take out of solution and drop to line for exact measurement
41
Give the steps to do a titration
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
What are the two main indicators for acid/alkali reactions?
Methyl orange - yellow to red when adding acid to alkali | Phenolphthalein - red to colourless when adding acid to alkali
43
How can you obtain g dm-3 from the mol dm-3?
g dm-3 = mol dm-3 x Mr
44
What is the calculation for volume?
volume (cm3) = moles x 1000 / concentration
45
What are the assumptions of an ideal gas?
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
Which gases behave like ideal gases?
Those which are well above their boiling points | Nitrogen, oxygen, hydrogen and noble gases
47
How do you convert different volumes?
1 m3 = 1000 dm3 = 1000000 cm3

A Level - Chemistry (26 decks)

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