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A-LEVEL CHEM 3.1: Physical Chemistry > A-LEVEL Chemistry: 3.1.2: Calculations > Flashcards

A-LEVEL Chemistry: 3.1.2: Calculations Flashcards

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1
Q

What is a ‘Mole’?

A

The Mole is the Amount of a Substance in Grams that has the Same Number of Particles as there are Atoms in 12g of a C12 Atom.

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2
Q

There are ___ Atoms in 12g of C12. This Number is Called…

A

6.022x10^23. Avogadro’s Constant.

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3
Q

What is ‘Relative Atomic Mass’?

A

Relative Atomic Mass is the Average Mass of One Atom, Compared to 1/12th the Mass of One Atom of C12.

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4
Q

What is ‘Relative Molecular Mass’?

A

Relative Molecular Mass is the Average Mass of a Molecule, Compared to 1/12th the Mass of One Atom of C12.

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5
Q

Moles = …

A

Mass / Mr

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6
Q

Pressure * Volume = …

A

Moles * R(8.31) * Temperature

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7
Q

How do you Convert Degrees Celsius (‘C) to Kelvin (K)?

A

Add 273.

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8
Q

Concentration = …

A

Moles / Volume

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9
Q

Cm^3 —–> dm^3 = …

A

/1000

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10
Q

How Many Significant Figures Should your Answer be Given to in A-Levels?

A

Give your Answer to the Same Number of SigFigs as the Value Given in the Question with the Least Amount of SigFigs.

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11
Q

What is ‘Avogadro’s Constant’?

A

6.022 x 10^23

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12
Q

Density = …

A

Mass / Volume

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13
Q

Density is Usually Given in…

A

g cm^-3

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14
Q

Especially in A-Levels, you Must take Care with…

A

Units.

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15
Q

What is ‘Empirical Formula’?

A

The Empirical Formula is the Simplest Ratio of Atoms of Each Element in the Compound.

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16
Q

What is the ‘Empirical Formula’ of a Chemical Reaction?

A

The Empirical Formula of a Chemical Reaction is the Simplest Ratio of Atoms of Each Element in the Chemical Reaction.

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17
Q

What is ‘Molecular Formula’?

A

A Molecular Formula is the Actual Number of Atoms of Each Element in the Compound.

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18
Q

The Mr of a Substance Can be found out by Using a…

A

Mass Spectrometer. The Molecular Ion (the Peak with the Highest m/z) Will be Equal to the Mr.

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19
Q

What is a ‘Hydrated Salt’?

A

A Hydrated Salt Contains Water of Crystallisation.

20
Q

Method for the Practical: ‘Heating in a Crucible’. (6)

A

-Weigh an Empty Clean Dry Crucible & Lid.

-Add 2g of Hydrated Calcium Sulfate to the Crucible, & Weigh it again.

-Heat Strongly with a Bunsen Burner for a Couple Minutes.

-Allow to Cool.

-Weigh the Crucible & Contents again.

-Heat the Crucible again, & Reweigh Until you Reach a Constant Mass (do this to Ensure that the Reaction is Complete- nothing is Left in Excess).

21
Q

Large Amounts of Hydrated Calcium Sulfate (e.g. 50g) Should Not be Used in the ‘Heating in a Crucible’ Practical. Why is this?

A

This is Because the Decomposition is Likely to be Incomplete.

22
Q

In the ‘Heating in a Crucible’ Practical, why Must the Crucible be Dry?

A

The Crucible Needs to be Dry, Otherwise a Wet Crucible Would Give an Inaccurate Result. It Would Cause a Mass Loss to be too Large, as the Water Would be Lost when Heating.

23
Q

In the ‘Heating in a Crucible’ Practical, how does the Lid Improve the Accuracy of the Experiment?

A

The Lid Improves the Accuracy of the Experiment, as it Prevents the Loss of Solid from the crucible, but Should be on Loose, Allowing Gas to Escape.

24
Q

What is a ‘Solution’?

A

A Solution is a Mixture Formed when a Solute Dissolves in a Solvent. (e.g. Salt Dissolving in Water).

25
Q

Molar Concentration Can be Measured for…

A

Solutions.

26
Q

Conc. = …

A

Mol. / Vol.

27
Q

The Concentration of a Solution Can also be Measured in terms of…

A

Solute Per Volume of Solution.

28
Q

Mass Concentration = …

A

Mass / Volume

29
Q

When Soluble Ionic Solids Dissolve in Water, what happens?

A

When Soluble Ionic Solids Dissolve in Water, they Will Dissociate into Separate Ions. This Can Lead to the Concentration of Ions Differing from the Concentration of the Solute.

30
Q

When Soluble Ionic Solids Dissolve in Water, they Will Dissociate into Separate Ions. What Can this Lead to?

A

This Can Lead to the Concentration of Ions Differing from the Concentration of the Solute.

31
Q

Diluting a ___ Will Not Change the Amount of Moles of ___ Present, but it Will Increase the ___ of Solution, & Hence the Concentration Will ___.

A

Solution, Solute, Volume, Decrease.

32
Q

Moles = Volume * Concentration

If the Amount of Moles doesn’t Change, then:

A

Original Volume * Original Concentration

New (Diluted) Volume * New (Diluted) Concentration

33
Q

What is the ‘Ideal Gas Equation’?

A

The Ideal Gas Equation Applies to All Gases & Mixtures of Gases. If a Mixture of Gases is Used, the Value n Will be the Total Moles of all Gases in the Mixture.

34
Q

Ideal Gas Equation:

A

PV = nRT

Pressure * Volume = Moles * 8.31JK^-1mol^-1 * Temperature

35
Q

What are ‘Gas Syringes’?

A

Gas Syringes Can be Used for a Variety of Experiments, where the Volume of a Gas is Measured, Possibly to Work out the Moles of Gas, or to follow Reaction Rates.

36
Q

What does the Volume of Gas depend on?

A

The Volume of Gas depends on Pressure & Temperature.

37
Q

The Volume of Gas Depends on Pressure & Temperature. So, when Recording the Volume of a Gas, it is Important to note down the… (2)

A

-The Temperature of the Room.

-The Pressure of the Room.

38
Q

Potential Errors in Using a Gas Syringe: (3)

A

-Gas Escapes before the Bung is Inserted.

-The Syringe Sticks.

-Some Gases, eg CO2, are Soluble in Water, so the True Amount of Gas is Not Measured.

39
Q

Equal Volumes of Any Gases, Measured Under the Same Conditions of Temperature & Pressure, Contain Equal Numbers of…

A

Moles (or Atoms, if the Gas is Monatomic).

40
Q

Volumes of Gases Reacting in a Balanced Equation Can be Calculated by…

A

Finding a Simple Ratio, & Calculating as normal.

41
Q

Converting Quantities Between Different Substances Using a Balanced Equation: (3)

A

-Equations Required:
Moles = Mass / Mr (for Pure Solids, Liquids, & Gases)

PV = nRT (for Gases)

Conc. = Mol. / Vol. (for Solutions)

  • 1) Use one of the above Equations to Convert any Given Quantity into Moles.
  • 2) Use a Balanced Equation to Convert Moles of Initial Substance into Moles of the Second Substance.
  • 3) Convert Moles of Second Substance into the Quantity that the Question asked for, Using the relevant Equation.
42
Q

Percentage Yield = …

A

Actual Yield / Theoretical Yield (*100%)

43
Q

% Atom Economy = …

A

Mass of Useful Products / Total Mass of Reactants (*100%)

44
Q

The Method for the Practical ‘Titrations’: (

A

-Rinse Equipment (Burette with Acid, Pipette with Alkali, Conical Flask with Distilled Water).

-Pipette 25cm^3 of Alkali into the Conical Flask. (Pipette should only Touch the Surface of the Alkali to Ensure that the Correct Amount is Added).

-Fill the Burette with the Acid until the Meniscus Reaches 0.

-Add 1-2 Drops of (Phenolphthalein) Indicator to the Alkali in the Conical Flask. The Colour should Change to Pink.

-Put the Flask Under the Burette Tap & Slowly Start Letting Acid Pour Out. Keep on Swirling the Conical Flask (which has the Alkali in it).

-Keep Pouring Acid Out & Swirling Until the Colour Changes from Pink to Colourless.

-Note the Burette Reading.

-Repeat the entire Titration Practical Until at least 2 Concordant Results are Obtained (2 Reading Within 0.1cm^3 of each other). At this point, we say that the Titration Technique is good/consistent.

45
Q

When Working Out the Average Titre Results from your Titration Results, …

A

Only Calculate the Average Using the Concordant Results.
This is Because they are taken to be the Results that come from a good/consistent Titration Technique, hence are more trustworthy.

A-LEVEL CHEM 3.1: Physical Chemistry (2 decks)

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