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Chemistry > Unit 14, 15 & 16 - Quanititative analysis/ Dynamic Equilibra, Calculations Involving Volumes Of Gases/ Chemical Cells And Fuel Cells > Flashcards

Unit 14, 15 & 16 - Quanititative analysis/ Dynamic Equilibra, Calculations Involving Volumes Of Gases/ Chemical Cells And Fuel Cells Flashcards

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1
Q

What is the theoretical yield?

A

The maximum mass of product that can be formed from a reactant.

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2
Q

What is the actual yield?

A

The amount of product obtained when you carry out an experiment.

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3
Q

What is the percentage yield?

A

It compares the actual yield and the theoretical yield

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4
Q

What does the theoretical yield assume?

A

That all the reactants are turned into products and the products are successfully separated from the reaction mixture.

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5
Q

Give 3 reasons why reactions do not give 100% yields

A

Incomplete reaction - not all reactants are used up
Some product is lost - some left behind in container
Unwanted side reactions - other products formed

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6
Q

Why is a higher yield better?

A

Fewer raw materials are used to make the same amount of product, more useful reaction.

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7
Q

What is atom economy?

A

A method of showing how efficient a particular reaction is at making use of the atoms in the reactants

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8
Q

Give an example of a reaction with 100% atom economy

A

Ethene + steam —> ethanol

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9
Q

Why does the production of ethanol by fermentation of sugars have a lower atom economy?

A

It produces carbon-dioxide as a by-product

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10
Q

Give a way to improve the atom economy of a reaction

A

To find uses fro the by-products

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11
Q

Give 2 reasons why chemists might choose to use fermentation for ethene production

A

Only 30-40 degrees needed

Uses renewable resources

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12
Q

Give 2 reasons why chemists would use a steam reaction to produce ethene

A

Fast

Creates pure ethene

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13
Q

What is a volumetric flask?

A

The apparatus used to make a solution with an accurate concentration

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14
Q

How do you make a solution using a volumetric flask

A

The solute is dissolved in distilled water, then made up to the graduation mark before stoppering and shaking the flask

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15
Q

What does it mean to measure from the bottom of the meniscus

A

To measure the reading from the lowest point of the ‘bowl’ shape of the solution

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16
Q

What is 1dm^3 the same as in cm

A

1000cm^3

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17
Q

What are acid-alkali titrations used to find

A

The exact volume of an acid that neutralises a specific volume of alkali or vice versa

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18
Q

What does the volume occupied by a sample of a gas depend on?

A

The temperature, pressure and number of particles of gas

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19
Q

What does Avogadro’s law state about gas volume

A

If the temperature and pressure are the same, equal volumes of different gases contain an equal number of molecules

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20
Q

What is the molar volume?

A

The volume occupied by one mole of molecules of any gas

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21
Q

What is the molar volume at room temperature and pressure (rtp)?

A

24 dm^3

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22
Q

How do plants absorb water and mineral ions?

A

Through their root hair cells

23
Q

What happens if plants don’t get enough water or minerals

A

They can have defiance diseases such as stunted shoots and discoloured leaves

24
Q

What is the role of fertilisers

A

To replace the mineral ions needed by the plants and to promote plant growth

25
Q

What are the 3 elements found in artificial fertilisers?

A

Nitrogen, phosphorus, potassium

26
Q

What are nitrogenous fertilisers

A

A source of soluble nitrogen compounds

27
Q

Give 2 examples of a nitrogen-rich fertiliser

A

Ammonium nitrate, ammonium sulphate

28
Q

What is the word equation for the production of ammonium nitrate

A

Ammonia + nitric acid —> ammonium nitrate

29
Q

What is the symbol equation for the production of ammonium nitrate

A

NH3 + HNO3 —> NH4NO3

30
Q

What process is ammonia manufactured by?

A

The Haber process

31
Q

What is the word equation for the production of nitric acid from ammonia?

A

Ammonia + oxygen —> nitric acid + water

32
Q

What is the word equation fo the production of ammonium sulphate?

A

Ammonia + sulphuric acid —> ammonium sulphate

33
Q

Give 2 differences about preparing ammonium sulphate in the laboratory - industrial

A

Small scale - large scale

Batch - continuous

34
Q

How is ammonium sulphate made industrially?

A

Through many stages

35
Q

When does a reversible reaction reach an equilibrium

A

When they are in a closed system ( stoppered flask, nothing can escape)

36
Q

What are 2 factors of dynamic equilibriums

A

The forward and backward reactions are at the same rate

The concentrations of all reacting substances do not change

37
Q

Which direction does the position of the equilibrium move when something is altered?

A

To oppose any changes made

38
Q

If the temperature is increased, which direction does the equilibrium move to?

A

Toward endothermic reaction (this takes in heat which opposes the added heat)

39
Q

If the pressure is increased , which direction does the equilibrium move to?

A

Towards less molecules, to speed up this reaction to counteract the added molecules

40
Q

If the concentration is increased , which direction does the equilibrium move to?

A

Towards lower concentration to even out the concentrations

41
Q

Why might manufacturers not be able to use reactions that reach equilibrium?

A

It can take too long

42
Q

What is the word equation for the Haber process?

A

Nitrogen + hydrogen —> ammonium

43
Q

What is the symbol equation for the Haber process?

A

N2 + 3H2 —> 2NH3

44
Q

How many atmospheres is the pressure chosen for the Haber process?

A

200 atmospheres

45
Q

What is the temperature chosen for the Haber process?

A

450 degrees Celsius

46
Q

Why does the Haber process not use high pressures or low temperatures?

A

Too expensive, too slow

47
Q

Why is an iron catalyst used for the Haber process?

A

It’s doesn’t change the position of the equilibrium but it does speed up the reaction.

48
Q

Why might a particular reaction pathway be chosen? (3 factors)

A

Availability and cost of raw materials and energy supplies
Rate of reaction and equilibrium position
Atom economy, yield, usefulness of by-products

49
Q

If 2 metals are further away on the reactivity series in a circuit, what happens to the voltage

A

It is bigger

50
Q

What does chemical cells contain (2) (Daniell cell)

A

2 different metals in a solution of one of their salts

A ‘salt bridge’ to allow dissolved ions to pass over

51
Q

What type of reaction happens in Daniell cell

A

Exothermic, displacement

52
Q

What is the product of a hydrogen-oxygen fuel cell

A

Water

53
Q

How does a hydrogen-oxygen fuel cell work

A

Hydrogen on left side, oxygen on right side with electrodes with a membrane in between the electrodes.
H+ ion from H passes through membrane after attracted to electrode and 2 H+ bond to oxygen on other side

54
Q

Why do hydrogen-oxygen fuel cells still on involve CO2

A

When H is manufactured, CO2 is a by product

Chemistry (12 decks)

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