C4, Chemical Calculations Flashcards

1
Q

Formula for number of moles

A

Number of moles = mass / Ar or Mr

Mass in g
Ar = atomic mass
Mr = relative formula mass

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2
Q

Avogadro’s constant

A

6.02 x 10^23

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3
Q

What do balanced equations show

A

They tell you the number of moles of substances are involved in a chemical reaction

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4
Q

What does yield of a chemical reaction mean

A

How much product is made

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5
Q

Formula for percentage yield

A

Percentage yield = (actual mass of product produced / max theoretical mass of product possible) x 100%

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6
Q

Factors affecting percentage yield

A
  • product may be lost in handling / left in apparatus
  • the reaction may be reversible (as they form they react to reform the reactants)
  • some reactants may produce unexpected reactions
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7
Q

What is atom economy

A

The measure of the extent to which the atoms in the starting materials end up in the desired product

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8
Q

What happens if remaining atoms aren’t used up in other products (atom eco)

A

They end up as hazardous waste products

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9
Q

Formula for atom economy

A

% atom economy = (MR of desired product from equation / sum of the MR of the reactants from the equation) x 100%

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10
Q

Definition of concentrations

A

The amount of a substance dissolved in a given volume of liquid

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11
Q

Formula for concentration

A

Concentration = amount of solute / volume of solution

Concentration = g/dm^3
Amount of solute = g
Volume of solution = dm^3

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12
Q

What does a more concentrated solution have in comparison to a less

A

It has more solute in the same volume in comparison to a less concentrated solution

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13
Q

What are titrations used for

A

To measure accurately what volumes of acid and alkali react together completely

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14
Q

Titrations equation

A

Number of moles = concentration x volume / 1000

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15
Q

Titration method

A

1) using a pipette transfer 25cm^3 of an alkali into a conical flask?
2) add a few drops of a suitable indicator to the alkali
3) fill a clean dry burette with acid
4) note starting volume
5) add acid into the conical flask and swirl
6) when indicator starts to change colour add acid drop wise and swirl
7) when colour change lasts 10 secs stop adding acid and note the volume.
8) calculate titre and repeat until 2 concordant results are reached.

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16
Q

Volume of one mole of any gas

A

24dm^3

17
Q

Equation to find the mole of a gas

A

Number of moles of a gas = volume of gas (dm^3) / 24dm^3

18
Q

Molar gas volume

A

The volume of gas occupied by 1 mole of gas at room pressure and temperature