Topic 6 - Quantitive Analysis, Dynamic Equilibria, Calcularions Involving Volumes Of Gases, Chemical Cells and Fuel Cells

Question 1

actual yeild

Answer 1

The amount of product obtained when you carry out experiment

Question 2

Percentage yield equation

Answer 2

percentage yield = (actual yield / theoretical yield) x100

Question 3

reasons why the yield is less than expected

Answer 3

• reaction may be incomplete so not all the reactants are used up - possibly because the reaction has not been left for long enough or the reaction may reach equilibrium
• some of the products are lost
• there may be other unwanted side reactions taking place

Question 4

atom economy

Answer 4

mass of the product you want as a % of the mass of all the products you make

Question 5

atom economy equation

Answer 5

atom economy = (Relative formula mass of useful product /sum of relative formula masses of all the reactants) x 100

Question 6

% yeild

Answer 6

amount of product you actually make as a % of the amount you should theoretically make

Question 7

% yeild

Answer 7

amount of product you actually make as a % of the amount you should theoretically make

Question 8

How do you make a solution?

Answer 8

The solid is dissolved in distilled water and then made up to graduation mark before suffering and then shaking the flask

Question 9

Concentration of a solution

Answer 9

The amount of solute dissolved in a state volume of solution

Question 10

In centimetres cubed, how much is 1 decimetre cubed?

Answer 10

1000cm3 = 1dm3

Question 11

How do you work out concentration in g/dm3?

Answer 11

concentration in g/dm3 = mass of solute in g / volume of solution in dm3

Question 12

how do u work out concentration in mol/dm3 (2 equations)

Answer 12

concentration in mol/dm3 = number of moles of solute / volume of solution in dm3

concentration in mol/dm3 = concentration in g/dm3 / RFM of solute

Question 13

Acid-alkali Titration

Answer 13

Used to find the exact volume of an acid that neutralises a fixed volume of alkali or vice versa

Question 14

method for an acid-alkali titration (CORE PRACTICAL)

Answer 14

1. Rise a burette with hydrochloric acid to fill the burette with the acid
2. Record initial volume of the acid in the burette
3. Rinse pipette with sodium hydroxide solution then fill the pipette to the 25.0cm3 mark and empty the solution in a conical flask
4. Add a few drops of methyl orange indicated to the flask on a white tile underneath the burette
5. At the acid to the sodium hydroxide solution while swirling the flask
6. When the indicator starts to change colour rinse the tip of the burette and the sides of the flask with a small amount of distilled water from a wash bottle to ensure that all the acid is in the mixture and add the acid drop by drop until the end point is reached.
7. Record the final volume of acid in the burette
8. Repeat the experiment apart from the initial rinsing of the burette and pipette until concordant results are obtained.

Question 15

concordant result

Answer 15

if the results are within 0.2cm3 of each other

Question 16

End point

Answer 16

The point at which the indicator changes colour in an acid- base titration

Question 17

Avogadros Law

Answer 17

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

Question 18

Molar gas volume

Answer 18

The volume occupied by one mole of molecules of any gas (24dm3 at room temp and pressure)

Question 19

amount of gas equation (at rtp)

Answer 19

moles of gas = volume of gas (dm3) / 24

Question 20

How is ammonia manufactured?

Answer 20

Through the Haber process

Question 21

Haber process

Answer 21

Process in which nitrogen and hydrogen reacts together in a reversible reaction

Question 22

ammonia symbol equation

Answer 22

Question 23

What conditions are used in the Haber process?

Answer 23

• 450°C
• 200 atmospheres pressure
• iron catalyst

Question 24

What happens to the equilibrium position when temperature is increased?

Answer 24

The equilibrium position shifts in the direction of the endothermic reaction

Question 25

What happens to the position of equilibrium if pressure is increased in a reaction involving gases?

Answer 25

The position of equilibrium moves towards the side of the balanced equation with the fewer molecules of reacting gas

Question 26

What happens to the position of equilibrium if the concentration of a reacting substance increases?

Answer 26

The position of equilibrium moves away from the reacting substance in the balance equation

Question 27

What factors affect equilibrium?

Answer 27

- temp. - pressure - concentration

Question 28

When making ammonia is the forward reaction exo or endothermic

Answer 28

Exothermic

Question 29

When making ammonia is the backward reaction exo or endothermic

Answer 29

Endothermic

Question 30

When making ammonia why is it at 450°C?

Answer 30

Because low temperatures increase the equilibrium yield of ammonia but reduces the rate of reaction so 450°C is a compromise that gives an acceptable yield of ammonia in an acceptable time

Question 31

When making ammonia, why is it done at 200 atmospheres (pressure)?

Answer 31

High pressures increase equilibrium of ammonia and increase the rate of reaction so 200 atm is a compromise because it’s very high pressure too expensive to maintain

Question 32

When making ammonia, why is there an iron catalyst?

Answer 32

Because it does not change position of equilibrium, but it does increase the rate of reaction

Question 33

How is your reaction pathway chosen - what factors does it take into account?

Answer 33

- Availability and cost of raw materials and energy supplies - The rate of reaction and the equilibrium position - Atom economy, yield and usefulness of byproducts

Question 34

What is a byproduct?

Answer 34

An accidental or secondary product made in the manufacture of synthesis or something else

Question 35

What components does a chemical cell contain?

Answer 35

- 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 another

Question 36

What does it mean to the voltage if the two metals are further apart in the reactivity series? (Chemical cell)

Answer 36

The voltage is greater when the two metals are further apart in the reactivity series

Question 37

What three elements do plants need to grow well?

Answer 37

- Nitrogen, phosphorus and potassium

Question 38

Artificial fertilisers (NPK fertilisers)

Answer 38

chemical compounds which contain these elements - they need to be soluble so that the ions dissolve and are easily absorbed by plant

Question 39

How are ammonium salts made?

Answer 39

A neutralisation of ammonia with acids

Question 40

Haber process diagram

Answer 40

Question 41

What ammonium salts are used as fertilisers?

Answer 41

- Ammonium sulphate and ammonium nitrate

Question 42

What is a batch process?

Answer 42

A method of completing tell us all the groups or a lot rather than individually or in real time

Question 43

What do fertilisers do?

Answer 43

They replace the mineral ions needed by plants and so promote plant growth

Question 44

hydrogen fuel cells

Answer 44

are electrochemical devices like batteries, which produce electricity by converting hydrogen and oxygen into water

Question 45

Fuel cell

Answer 45

Electricity produced when they are supplied with fuel and oxygen from outside

Question 46

What happens at each electrode in a hydrogen-oxygen fuel cell?

Answer 46

- hydrogen atoms lose electrons and form hydrogen ions - electrons flow through the external circuit to the positive electrode (anode) - hydrogen ions pass through a membrane to the right hand side electrode where they gain electrons and react with oxygen to produce water

Question 47

How do you calculate the theoretical yield?

Answer 47

Calculate the relative formula masses and a multiplied by the balancing number (total RFM)

Question 48

What are the two methods of making ethanol

Answer 48

- fermentation - Reaction of ethene w steam

Question 49

Compare fermentation and reaction of ethene with steam

Answer 49

Question 50

What is a continuous process?

Answer 50

A process in which reactants are constantly fed into the reactors and products are removed

Question 51

Advantages of continuous process

Answer 51

+ automated - need fewer people to make a given amount of product

Question 52

daniell cell

Answer 52

an electrochemical cell that converts chemical energy into electrical energy

Question 53

How is hydrogen mostly manufactured?

Answer 53

by the reaction of steam with coal or natural gas -> these processes do release carbon dioxide as a byproduct

Question 54

when increasing temp, what happens to the yield of products and rate of reaction

Answer 54

idk

Question 55

when increasing pressure, what happens to the yield of products and rate of reaction

Question 56

when increasing conc, what happens to the yield of products and rate of reaction

Question 57

explain why the mixture is stirred

Answer 57

so that the mixture is evenly mixed to help the elements to collide and react to see the change of colour

Question 58

explain the effect of any that traces of water in the pipette after rinsing could have on the titration result

Answer 58

- less hydroxide used -> more dilute - less acid used in titration -> titration result decreased

Question 59

explain the effect of any that traces of water in the conical flask after rinsing could have on the titration result

Answer 59

no change in volume or conc of hydroxide solution added to flask -> no change in result

Question 60

state the colour change of phenolphthalein at the end point when the barium hydroxide solution has just be neutralised

Answer 60

pink to colourless

Question 61

describe an experiment to obtain a sample of pure dry barium sulphate from the contents of the conical flask after a titration

Answer 61

- filter the barium sulphate (precipitate) - wash precipitate with water - dry precipitate in warm oven on filter paper