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A LEVEL CHEM > Topic 5-Formulae, Equations & Amounts of Substances > Flashcards

Topic 5-Formulae, Equations & Amounts of Substances Flashcards

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1
Q

Give the definition of the Empirical Formula

A

The smallest whole number ratio of the atoms of each element in a compound.

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2
Q

If you have 5cm, how many dm will you have?

A

0.005dm

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3
Q

What does Avogadro’s constant tell you? What is the figure?

A

The number of particles in a mole, 6.02 x 10^23

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4
Q

Give the definition for the molecular formula.

A

The molecular formula gives the actual numbers of atoms of each type of element in a molecule.

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5
Q

What is a base?

A

Bases are substances that act as the opposite of acids, they also release hydroxide ions in aqueous solutions.

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6
Q

A solution of sodium hydroxide is described as having a concentration of 0.4 mol dm-3. Explain what this means.

A

0.4 mols of sodium hydroxide are dissolved in every dm3 of solution.

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7
Q

What number must you add to the degrees in C to get the degrees in Kelvin?

A

273

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8
Q

What equation can you use for % uncertainty?

A

(uncertainty/measurement) x 100 x no.of measurements

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9
Q

What will form when a reactive metal + acid react?

A

Salt + Hydrogen

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10
Q

What will form when you react an acid and a base?

A

Salt + water

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11
Q

What reactants will produce salt + water + carbon dioxide?

A

Acid + carbonate

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12
Q

Define the concentration of a solution.

A

How many moles/grams are dissolved per 1dm”3

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13
Q

What are the units for concentration?

A

g dm-3
or
mol dm-3

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14
Q

What type of reaction has taken place if two aqueous solutions react to form a solid?

A

A precipitation reaction i.e solid precipitate has formed.

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15
Q

What is the only thing ionic equations show?

A

Only the reacting particles (and products they form)

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16
Q

Define Molar gas volume.

A

The space one mole of gas occupies at a certain temp and pressure.

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17
Q

What is the volume of 1 mol of gas at room temperature and pressure?

A

24dm”3 mol-1

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18
Q

What is the volume of 1 mol of gas at standard temperature and pressure?

A

22.4dm”3 mol-1

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19
Q

What is the IDEAL gas equation?

A

PV=nRT

20
Q

What is a hazard?

A

Anything that has the potential to cause harm or damage.

21
Q

What is risk?

A

The probability of someone or something being harmed if they are exposed to the hazard

22
Q

Define systematic error

A

These errors are the same every time you repeat the experiment e.g. set up of equipment.

23
Q

Define a random error

A

These errors are different every time you repeat the experiment e.g. error reading burette.

24
Q

Which type of error can be reduced by repeating the experiment?

A

The random errors.

25
Q

If the conical flask is washed out between each titrations, will this effect the moles?

A

No this has NO EFFECT on mols.

26
Q

How will the experiment be affected if the pipette is washed out with water before each titration?

A

It will dilute what is in the conical flask so titres will be smaller.

27
Q

What effect will completely filling the volumetric flask rather than it only being to the graduation line, have?

A

Solution in the burette will be too dilute therefore titre will be larger than it should be.

28
Q

How do you know what is ionic?

which ions become disassociated

A

Roughly-
Metal (or ammonium) compounds. Acids in solution = ionic (only split up ions if it’s aqueous)
anything else e.g. insoluble salts. = not ionic

29
Q

How do ionic equations for acids and metal hydroxides differ?

A

All ions disassociate so in the end its always a reaction between
H + OH –> H2O

30
Q

What happens in ionic equations for the reaction between acids and metal carbonates?

A

It will ALWAYS be

CO3 + 2H —-> CO2 + H2O

31
Q

Even in net ionic equations, only which type of element should have a charge?

A

AQUEUOUS atoms are only ever written with a charge.

Leave gases and solids neutral!!!

32
Q

What should you do with the conical flask to ensure the results of the experiment aren’t affected

A

rinse with distilled or deionised water.

33
Q

Equation for atom economy?

A

mass of atoms in desired product/

mass in all reactants x100

34
Q

Equation for percentage yield?

A

actual yield/ maximum theoretical yield x 100

35
Q

Define “mole”

A

One mole is the amount of substance that contains the same number of particles as the number of carbon atoms in 12g of C12.

36
Q

What can you know about an equation involving a basic oxide?

A

That a basic oxide acts oppositely to an acid

37
Q

When are your results labelled as “concordant”

A

When they are within 0.1 of each other (NOT INCLUDING ROUGH TITRE)

38
Q

In a question you know that two compounds are in a 1:1 ratio. How do you work out the percentage yield of the compound?

A

As it is in 1:1 ratio, this mean that the THEORETICAL YIELD is equal to this number of mols. Then rearrange the equation.

39
Q

Define the term ‘mole’

A

One mole is amount of substance that contains that contains the same number of particles as the number of carbon atoms in exactly 12g of carbon 12

40
Q

What are the units for molar mass?

A

g mol-1

LITERALLY MR THINK G / MOL

41
Q

Explain 3 actions the technician might take in the procedure just before the end point of titration to ensure end point accurate

A
  • White tile to accurately see point of colour change
  • Drop by drop when closer to rough titre TO AVOID OVERSHOOTING
  • swirl to ensure all alkali and acid react.
42
Q

In a question where they use a 100cm3 solution and then only put 10cm3 into conical flask remember…..

A

To divide the moles by 10!

10/100 of solution so not representational of just 10!

43
Q

How does a graph show direct proportion?

A

Straight line through origin.

44
Q

Why would you add a pinch of Xcarbonate to acid before the reaction

A

To saturate solution with CO2.

45
Q

What happens to a solution during a dilution?

A

Will increase the volume, and decrease the concentration but the moles will stay the same.

46
Q

What is 1000 mg in g?

A

1g = 1000mg

47
Q

How many kg in 1 tonne?

A

1000kg

A LEVEL CHEM (34 decks)

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