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A Level Chemistry > Formulae And Amounts > Flashcards

Formulae And Amounts Flashcards

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1
Q

Calculate moles when mass is given

A

Moles= mass/molar mass (RFM)

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2
Q

Calculate moles in a solution

A

Moles = concentration x volume

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3
Q

Calculate moles in gas at room temperature and pressure

A

Volume = moles x 24

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4
Q

Cm3 into dm3

A

Divide by a 1000

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5
Q

Calculate gas at any temperature or pressure and give the SI units for each component also known as ideal gas equation

A 
PV=nRT
Pressure in pascals (kPax1000)
Volume in dm3
N=number of moles 
R=8.31 
T=temp in Kelvin (Celsius plus 273)
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6
Q

Avagado calculations

A

Moles x 6.02x10 to the power of 23 = number of molecules

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7
Q

Empirical formula table headings (vertically)

A 
Horizontally is the elements
Mass or %
RFM 
Moles
Divide by the smallest
Ratio
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8
Q

Combustion analysis

A

😓

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9
Q

General procedure for mole calculations

A 
Balanced equation 
Write what you know under each species 
Convert to moles where possible 
Use molar ratio (stoichiometry) to find where you’re going 
Convert into asked units
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10
Q

Find molecular formula

A

Empirical formula mass then divide by given mass and multiply each element in compound by the scale factor

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11
Q

Mole definition

A

Amount of substance that contains the same number of particles as 12g of Carbon - 12 isotope

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12
Q

Mass concentration equation

A

Mass of solute divided by volume of solvent

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13
Q

Molar concentration equation

A

Rearranging concentration x volume = moles to get concentration = moles divided by volume

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14
Q

What is a standard solution?

A

A solution whose concentration is accurately known.

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15
Q

What are primary standards?

A

Substances used to make a standard solution by weighing.

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16
Q

Primary standards criteria:

A 
Solids with high molar masses
High purity 
Chemically stable 
React rapidly and completely with other substances used in titrations 
 To abosorb water from the atmosphere
17
Q

Apparatus for making primary solution of sulfamic acid

A 
Accurate balance
Weighing bottle 
Spatula 
250cm3 beaker and volumetric flask 
Deionised water 
Funnel 
Glass stirrring rod
18
Q

How to prepare a primary solution of sulfamic acid

A

Add approximately 2.5g of sulfamic acid to the weighing bottle and record measurement then transfer acid to a beaker and weigh bottle again. Add 100cm3 of deionised water to beaker until all sulfamic acid is dissolved and stir with rod. Use deionised water to wash all traces of acid from rod into beaker. Then place funnel in volumetric flask and pour solution from beaker. Rinse the inside of the beaker several times and transfer findings to flask. Add deionised water to flask and make it up exactly to the graduation mark. Put stopper and invert half a dozen times to make a uniform solution.

19
Q

What is the aim of titration

A

Measuring the volumes of two solutions that react together can also be known as volumetric analysis

20
Q

Titration method

A

Rinse the conical flask with deionised water on a white tile
Use a pipette fillers and rinse the pipette with deionised wafer and then with some of sodium hydroxide
Use the pipette to transfer 25cm3 of sodium hydroxide to the conical flask
Add three drops of methyl orange
Rinse the burette with deionised water and then with some sulfamic acid solution
Fill burette with sulfamic acid and set it up above the conical flask
Record initial burette reading
Add sulfamic acid to the conical flask until the indicator just changed colour and again record burette reading
Empty and rinse conical flask with deionised water and repeat till concordant titres are obtained

21
Q

Concordant titres

A

Each with thing 0.1cm3 of each other and all together 0.2cm3

22
Q

Methyl orange colour changes and works well with what combinations of acids and bases

A

Red in acid
Yellow in alkali
Pink in neutral

Strong acid weak bade
Strong acid strong base

23
Q

Phenolphthalein colour changes and acid base combinations

A

Colourless in acid
Pink in alkali

Weak acid strong base
Strong acid strong base

24
Q

Examples of strong acids are:

A

HCl

HNO3

25
Q

Examples of strong bases:

A

NaOH

KOH

26
Q

Commonest weak acid and commonest weak base

A

Ethanoic acid

Ammonia

27
Q

A student does not fill the space between tip and tap of burette. Explain the effect on the titre value.

A

The tire value would be more than in reality

A Level Chemistry (8 decks)

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