Topic 5 - Amount of Substance

Question 1

What is Avogadro constant

Answer 1

number of particles in one mole is 6.02 x 10^23

Question 2

what is molar mass

Answer 2

the relative molecular mass

Question 3

how to work out number of moles

Answer 3

moles = mass / Mr

Question 4

what is concentration

Answer 4

how many moles are dissolved per 1 dm^3 of solution

Question 5

what is concentration measured in

Answer 5

mol dm^-3

Question 6

how to work out moles with concentration

Answer 6

moles = conc. x volume

Question 7

what is empirical formula

Answer 7

the smallest whole number ratio of atoms of each element in a compound

Question 8

what is molecular formula

Answer 8

the actual number of atoms of each type of element in a molecule

Question 9

what to work out % composition

Answer 9

mass of element / total mass

Question 10

what is an ionic equation

Answer 10

shows the reacting particles

Question 11

what does an ionic equation show

Answer 11

the reaction stoichiometry

Question 12

what is reaction stoichiometry

Answer 12

the ratios of reactants to products

Question 13

what is a displacement reaction

Answer 13

when a more reactive element reacts to take the place of a less reactive element in a compound

Question 14

what are the products when a base reacts with an acid

Answer 14

salt and water

Question 15

what is the molar gas volume

Answer 15

space that 1 mole of gas occupies at a certain pressure & temperature

Question 16

how much is r.t.p

Answer 16

24 dm^3 mol^-1

Question 17

how much is s.t.p

Answer 17

22.4 dm^3 mol^-1

Question 18

how to work out moles with molar gas volume

Answer 18

moles = volume / molar gas volume (r.t.p or s.t.p)

Question 19

long equation

Answer 19

PV = nRT

Question 20

what is the value of R in the PV = nRT equation

Answer 20

8.31

Question 21

what is a hazard

Answer 21

the potential to cause harm/damage

Question 22

what is a risk

Answer 22

the probability of someone being harmed if they are exposed to the hazard

Question 23

what is the risk assessment

Answer 23

how likely it is that something could go wrong, how serious it would be if it did, and ways to reduce the risk

Question 24

what is titration

Answer 24

it allows you to find out exactly how much acid is needed to neutralise a quantity of alkali

Question 25

what is uncertainity

Answer 25

due to the limits to sensitivity of equipment used

Question 26

how to work out % uncertainty

Answer 26

% uncertainty = (uncertainty / reading) x 100

Question 27

state 2 ways to reduce uncertainty

Answer 27

- by using the most precise equipment you can - by planning an experiment involving larger volumes of liquid

Question 28

what are the 2 types of errors that can be caused

Answer 28

- systematic - random

Question 29

what is a systematic error

Answer 29

caused by the set-up or equipment (the same every time you repeat the experiment)

Question 30

what is a random error

Answer 30

caused when reading off a scale (different every time you repeat the experiment)

Question 31

how does repeating the experiment reduce the errors

Answer 31

reduces the random errors, by not the systematic errors

Question 32

what is the theoretical yield

Answer 32

the mass of a product that should be made if no chemicals are lost in the process

Question 33

how to work out % yield

Answer 33

% yield = (actual yield / theoretical yield) x 100

Question 34

what is atom economy

Answer 34

a measure of proportion of reactant that became part of the desired product

Question 35

how to work out atom % atom economy

Answer 35

% atom economy = (Mr of desired product / Mr of all products) x 100

Question 36

what is a substitution reaction

Answer 36

when atoms from one reactant swap with atoms from another reactant