formulae and amounts (2)

Question 1

what is a mole

Answer 1

amount of chemical species found in 12g of carbon 12

Question 2

what is Avogadros constant

Answer 2

the number of atoms in exactly 12g of carbon 12

(6.02 x 10^23 mol-1)

Question 3

what is molar mass

Answer 3

mass of one mole of the substance expressed in gmol-1

Question 4

what is empirical formula

Answer 4

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

Question 5

what is molecular formula

Answer 5

the actual number of atoms of each element in a compound

Question 6

what is a spectator ion

Answer 6

ions that do not take part in the reaction

Question 7

what does ‘hydrated’ mean

Answer 7

a compound that has molecules of water of crystallisation

Question 8

what is a solution

Answer 8

solvent (dissolves solute)

Question 9

what is a standard solution

Answer 9

the one with accurately known concentration

Question 10

what is mass concentration

Answer 10

mass of solute per volume of solution
(gdm-3)

Question 11

what is molar concentration

Answer 11

moles of solute per volume of solution (moldm-3)

Question 12

what is primary standard

Answer 12

a substance used for preparation of a standard solution by weighing

Question 13

what is Avogadros law

Answer 13

provided the conditions of temperature and pressure are the same, equal volume of gases contain the same number of molecules

Question 14

what is molar volume

Answer 14

the volume of 1 mole of gas

Question 15

what is a displacement reaction

Answer 15

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

Question 16

what is a precipitation reaction

Answer 16

one that produces an insoluble solid

Question 17

what is an error

Answer 17

a discrepancy between the value obtained in the experiment and an actual value

Question 18

what is precision

Answer 18

refers to how close to each other are the values obtained in an experiment

Question 19

what is accuracy

Answer 19

refers to how close the values are to the actual value

Question 20

what are concordant results

Answer 20

results that lie close to eachother
e.g titration +/- 0.10

Question 21

what is a margin of error

Answer 21

the range in which the true value of a measurement could lie
e.g burettes +/- 0.05

Question 22

what is a random error

Answer 22

they occur when conditions are varied in an unpredictable manner

Question 23

what is a systematic error

Answer 23

errors which are constant when you repeat an experiment. they usually are a result of the apparatus used

Question 24

what is the equation for percentage uncertainty

Answer 24

uncertainty/reading x100

Question 25

what is the equation for percentage yield

Answer 25

actual yield/theoretical yield x100

Question 26

equation for a mole of any substance

Answer 26

6.02x10^23 atoms/molecules

Question 27

equation for number of particles

Answer 27

Avogadros number x number of moles

Question 28

equation for moles

Answer 28

mass/Mr

Question 29

equation for conc (2)

Answer 29

mass/vol moles/vol

Question 30

what do carbonates produce in acid base reaction

Answer 30

salt water and carbon dioxide

Question 31

how to use molar gas vol to work out moles

Answer 31

mol= vol/molar gas vol

Question 32

what is molar gas vol at standard temperature and pressure

Answer 32

22.4 (273K and 101.3KPa)

Question 33

what is molar gas vol at room temp

Answer 33

24 (293K + 101KPa)

Question 34

what is the ideal gas equation

Answer 34

pv= nRT

Question 35

steps for making standard solution in titration

Answer 35

1) weigh amount of solid precisely using mass balance and plastic weighing boat 2) transfer solid from boat to a beaker, wash any solid left behind into beaker using deionised water 3) dissolve solid fully using deionised water and stir with glass rod 4) transfer solution to volumetric flask, using funnel to avoid spillage and rinse the beaker and glass rod into flask to make sure it has all transferred 5) fill to graduation line with deionised water, use pipette when it gets close to top 6) invert flask a few times with lid on to ensure it is thoroughly mixed

Question 36

what colour is phenolphthalein indicator

Answer 36

colourless when acidic and pink when alkali

Question 37

what colour is methyl orange indicator

Answer 37

yellow when acidic and red when alkali

Question 38

what is equation for percentage error

Answer 38

uncertainty/reading x100

Question 39

how can you reduce errors

Answer 39

using more precise equipment using larger volume of liquid

Question 40

what is atom economy equation

Answer 40

molecular mass of desired product/ molecular mass of all reactants x100

Question 41

why do companys prefer a high atom economy

Answer 41

-raw materials used more efficiently, more sustainable -produce less waste so benefits environment -less by-products so less time and money spent seperating these from desired product