Amount of substance

Question 1

What is a mole?

Answer 1

The amount of substance in grams that has the same number of particles as there are atoms in 12 grams of carbon 12.

Question 2

What is relative atomic mass?

Answer 2

The average mass of one atom compared to one twelfth of the mass of one atom of carbon 12

Question 3

What is relative molecular mass?

Answer 3

The average mass of a molecule compared to one twelfth of the mass of one atom of carbon 12

Question 4

How can you use the Avogadro’s constant to calculate the number of particles?

Answer 4

Number of particles = Number of moles * Avogadro’s constant

Question 5

What is the Avogadro constant?

Answer 5

One mole contains 6.022*10^23 particles

Question 6

How do you calculate the number of moles?

Answer 6

Moles = mass/relative molecular mass

Question 7

What is the Ideal Gas equation?

Answer 7

pV = nRT

Question 8

How do you convert temperature to Kelvin?

Answer 8

Kelvin = degrees centigrade + 273

Question 9

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

Answer 9

cm^3 = dm^3 /1000

Question 10

How do you convert from cm^3 to m^3?

Answer 10

m^3 = cm^3 /1000000

Question 11

How do you convert from dm^3 to m^3?

Answer 11

m^3 = dm^3 /1000

Question 12

What is the concentration of a solution?

Answer 12

The number of moles dissolved per 1dm^3.

Question 13

How do you calculate the number of mole using the concentration and volume of the solution?

Answer 13

Number of moles = concentration * volume/1000

Question 14

What are the units for the concentration of a solution?

Answer 14

mol dm^3

Question 15

What is the empirical formula?

Answer 15

The simplest ratio of atoms of each element in a compound

Question 16

What is the molecular formula?

Answer 16

The actual number of atom of each element in a compound

Made up of a whole number of empirical units

Question 17

What is the theoretical yield?

Answer 17

The mass of product that should be formed in a chemical reaction

Question 18

What is the actual yield?

Answer 18

The mass of product formed after the reaction and is always less than the theoretical yield

Question 19

Why is the actual yield always less than the theoretical yield?

Answer 19

Not all the starting chemicals react fully

Some chemicals are lost

Question 20

How do you calculate the percentage yield?

Answer 20

Percentage yield = Actual yield/theoretical yield * 100

Question 21

What does the percentage yield tell us?

Answer 21

Percentage yield tells us how wasteful a process is as it is based on how much product is lost during the process

Question 22

What is the atom economy?

Answer 22

Atom economy is a measure of the efficiency of a reaction

Question 23

How do you calculate the atom economy?

Answer 23

%Atom economy = molecular mass of desired product/sum of molecular masses of all reactants * 100

Question 24

Why do companies in the chemical industry try to use high atom economies?

Answer 24

High atom economy processes are better for the environment as there is less waste

Question 25

Why are high atom economy processes more sustainable?

Answer 25

They make more efficient use of raw materials

Question 26

Why are high atom economy processes less expensive?

Answer 26

Companies will spend less money on separating the desired product from the waste products

Question 27

What do titrations allow you to do?

Answer 27

Titrations allow you to work out the concentration of an acid or alkali

Question 28

Describe how you would find the concentration of an alkali or acid from a titration.

Answer 28

-Accurately pipette 25cm^3 of alkali into conical flask -Touch the surface of the alkali with pipette -Add a few drops of the appropriate indicator -Fill a burette with a standard solution of acid using a funnel at eye level -add the acid into the alkali whilst swirling the mixture add the acid dropwise at the endpoint -Repeat the experiment to get 2-3 concordant results

Question 29

What is a standard solution?

Answer 29

A solution that has a known concentration

Question 30

What are the two main indicators for acid/alkali?

Answer 30

Methyl orange | Phenolphthalein

Question 31

What colour does methyl orange become in acid/alkali?

Answer 31

Red in acid | Yellow in alkali

Question 32

What colour does phenolphthalein become in acid/alkali?

Answer 32

Colourless in acid | Pink in alkali

Question 33

How do you calculate the apparatus uncertainty?

Answer 33

Apparatus uncertainty = (error /measurement) * 100

Question 34

Describe how you would find the relative molecular mass of a substance in a titration.

Answer 34

- Calculate the moles of the acid in the solution - Find the ratio of acid/alkali to substance - Use the ratio to calculate the number of moles of the substance - Calculate the relative molecular mass(mass = Mr * moles)

Question 35

What happens when you increase the amount of equipment being used?

Answer 35

The total apparatus uncertainty increases

Question 36

How would you calculate the total apparatus uncertainty?

Answer 36

Add all the uncertainties of the equipment together

Question 37

How could you do to decrease the apparatus uncertainty?

Answer 37

- taking a large reading using the equipment | - using more sensitive equipment

Question 38

What factors affect volume?

Answer 38

temperature pressure number of moles

Question 39

Describe a method for making a solution

Answer 39

- Weigh a beaker using a top pan balance - Add the solid into the beaker and weigh them - Record the difference in mass - Add distilled water into the beaker - Stir with a glass rod until all has dissolved - Transfer the solution into a volumetric flask with washings using a funnel - Add water up to 250cm^3 - Place a lid on top - Shake the flask for the solution to mix

Question 40

Suggest a reason why repeating a titration makes the value for the average titre more reliable

Answer 40

- Anomalies can be eliminated - Concordant results can be collected - An average can be calculated

Question 41

What effect would an air bubble have on the value of the first titre?

Answer 41

The value would be higher than the true value

Question 42

What effect would an air bubble have on the average titre?

Answer 42

- No effect | - The titre value can be discarded

Question 43

Suggest ideas on how the overall technique can be improved when making a solution

Answer 43

- weigh by difference - wash the stirring rod/beaker after use - shake the final solution - make the sure the bottom of the meniscus touches the mark

Question 44

What are the potential errors in using a gas syringe?

Answer 44

gas escapes before bung is inserted syringe sticks some gases like carbon dioxide and sodium dioxide are soluble in water