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Science - continued > Quantitative Analysis > Flashcards

Quantitative Analysis Flashcards

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1
Q

What is a theoretical yield?

A

The maximum mass of product that can be formed the reactant

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2
Q

What is the actual yield?

A

The amount of product obtained when you carry out an experiment which is known as the actual yield

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3
Q

How do you find the theoretical yield for example for hydrogen from 36g of water?

A

Relative formula mass x the balancing numbers

2H20 = 2 x (1+1+16)= 36 (calculate this first), then, 2H2 = 2 x (1+1) = 4g

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4
Q

How do you work out the percentage change for yield?

A

actual yield / theoretical yield x 100

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5
Q

Give the three reasons why reactions don’t give 100% yields?

A
  • reaction may be incomplete so not all of the reactants are used up (the reaction has not been left long enough)
  • some of the product was lost (e.g on the walls of the container)
  • there may be unwanted side reactions (e.g reactants make a different product
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6
Q

What has to increase in order for the reaction to be more useful?

A

The percentage yield

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7
Q

What does a high yield mean, amount of materials-wise?

A

Fewer raw materials are supposed to make the same high yield, so there is less waste and more profit can be made

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8
Q

What is atom economy?

A

Method of showing how efficiently a particular reaction makes use of the atoms in the reactants (some reactant will not get used for the specific purpose it is being made for)

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9
Q

How do you figure out atom economy?

A

the relative formula mass of the useful product / sum of all relative formula masses of all the reactants x 100

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10
Q

What is a by-product?

A

Something that is produced during the production or destruction of something else

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11
Q

How do you work out the atom economy from a balanced equation?

A

The reactant’s Mr will be the sum of all relative formula masses of all the reactants and the Mr of the useful product you are looking at, will be formula mass of the useful product for the top of the equation. Then do the calculation using the formula

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12
Q

Why is it better to make use of the waste by-products?

A

It means that you can increase the atom economy, meaning you have more ‘useful products’ as you are making use of all the products

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13
Q

What factors need to be taken into consideration when deciding on a reaction pathway?

A
  • Energy consumption
  • Rate of reaction
  • Raw materials
  • Conditions are needed to produce a high yield if the reaction reaches equilibrium (such as temperature)
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14
Q

What is a volumetric flask?

A

They are calibrated to measure one volume of solution accurately

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15
Q

What two things should you do when accurately measuring the volume of solution at the graduation mark?

A

Measure from the bottom of the meniscus (the curve at the top of a solution) and make sure to measure at eye level to avoid random error

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16
Q

What is the concentration?

A

The amount of solute dissolved in a stated amount of solution

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17
Q

What is concentration measured in?

A

Gdm^-3

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18
Q

How do you work out concentration?

A

mass of solute (g) / volume of solution (dm^3)

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19
Q

How do you convert from cm^3 to dm^3

A

divide by 1000

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20
Q

How do you work out the concentration if you’re given the number of moles of solute?

A

number of moles of solute (mol dm^-3) / volume of solution (dm^3)

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21
Q

How do you work out the concentration in mol dm^-3

A

concentration (gdm^-3) / relative formula mass of solute

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22
Q

What is the mole ratio?

A

`The ratio in moles of the substances in a balanced equation

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23
Q

How do you work out the volume of a solution with a given volume of another

A
  1. Calculate the mole ratio from the balanced equation
  2. Calculate the number of moles of the solution of the known volume and concentration
  3. Use the balanced equation and mole ratio to find out the number of moles of acid that reacted
  4. Calculate the volume of ‘acid’ needed

PLEASE FIND WORKED EXAMPLE ON PAGE 115 TO HAVE A CLEARER UNDERSTANDING

24
Q

What does Avogadro’s law state?

A

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

25
Q

What is the molar gas volume?

A

The volume occupied by one mole of molecules of any gas.

26
Q

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

A

24 dm^3 or 24000cm^3

27
Q

How do you work out the volume of gas?

A

Amount of gas (mol) x molar volume

28
Q

How do plants absorb water and mineral ions?

A

Through their root hair cells

29
Q

What are two side effects of plants which suffer from deficiency diseases?

A

Discoloured leaves (mainly yellow) and stunted shoots

30
Q

What do fertilisers do?

A

They replace the mineral ions needed by plants to promote growth

31
Q

Which three elements are important to have as soluble compounds for plant fertilisers and why?

A

Nitrogen, Potassium and Phosphorous - have to be soluble in order for the root hair cells to absorb them since they only absorb mineral ions dissolved in distilled water

32
Q

How is ammonium nitrate salt made?

A

By reacting ammonia solution with dilute nitric acid

33
Q

How is nitric acid made?

A

By reacting ammonium and oxygen together to form nitric acid and water

34
Q

How do you make ammonium sulfate?

A

By reacting ammonia with sulfuric acid

35
Q

What is the scale of production, starting materials, stages and type of process for the laboratory preparation of ammonium sulfate?

A

A small scale of production
ammonia solution and dilute sulfuric acid
titration and then crystallisation
batch process

36
Q

What is the scale of production, starting materials, stages and type of process for the industrial preparation for ammonium sulfate?

A

large scale of production
raw materials for making ammonia and sulfuric acid
several stages
continuous process

37
Q

Explain what a batch process is.

A

A small amount of the product is made, the apparatus is cleaned, and then another small amount is made

38
Q

Explain what a continuous process is

A

Reactants are constantly fed into the reactors and products are removed. The reaction is only stopped when the equipment rarely needs to be cleaned or maintained

39
Q

What happens to the forward and backward reactions in dynamic equilibrium?

A

They still happen but at the same rate

40
Q

What happens to the concentrations during dynamic equilibrium?

A

The concentrations of all reacting substances do not change

41
Q

State what happens to the position of the equilibrium and the time taken to reach the equilibrium when:

  • temperature is increased
  • pressure is increased (reaction involving gases)
  • concentration is increased
  • catalyst added
A
  • Endothermic direction and the time decreases
  • Fewer molecules direction and time decreases
  • Moves away from the reaction substances in the balanced equation and time decreases
  • no change and time decreases
42
Q

What is the pressure and temperature of the production of ammonia?

A

200 atmospheres and 450 degrees

43
Q

Which reaction is endothermic and which reaction is exothermic?

A

Endothermic- backward

Exothermic- forward

44
Q

Which catalyst is used in the haber process and why?

A

Iron catalyst because it doesn’t change the position of the equilibrium and it increases the rate of reaction

45
Q

What is the name of the process that produces nitric acid?

A

Ostwald Process

46
Q

What is a reaction pathway?

A

When there is more than one way for a substance to be made and so you must decide which one to take

47
Q

Which factors have to be taken into consideration to choose the reaction pathway?

A
  • availability and cost of raw materials and energy supplies
  • the rate of reaction and equilibrium position
  • atom economy, yield and usefulness
48
Q

What components does a simple chemical cell have?

A
  • Two different metals, each dipped into a solution of one of their salts
  • A ‘salt bridge’ to allow dissolved ions to pass from one solution to the other
49
Q

What relationship do the voltage and the reactivity of the metals have with each other?

A

the further apart the metals are in the reactivity series, the greater the voltage

50
Q

What happens to the voltage when one of the reactants are used up?

A

The reaction stops and the voltage is no longer produced

51
Q

What are fuel cells?

A

Fuel cells are supplied with oxygen and fuel from outside - they don’t go flat, as they produce a voltage as long as there are reactants

52
Q

What are the reactants of a hydrogen-oxygen fuel cell and the products?

A

Reactants- hydrogen and oxygen

Product - water only

53
Q

Give two reasons why a hydrogen-oxygen fuel cell and electric motor is better than a petrol or diesel engine?

A
  • it is quieter

- needs less maintenance

54
Q

Why is a hydrogen-oxygen fuel cell still a hassle?

A

The hydrogen has to be stored in a tank

55
Q

Do the hydrogen-oxygen fuel cells produce greenhouse gases?

A

No, they don’t, but the manufacturing of the hydrogen releases carbon dioxide as a by-product which is a greenhouse gas (this is because it is made by reacting steam with coal or natural gas)

Science - continued (9 decks)

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