topic 5

Question 1

mole

Answer 1

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

Question 2

relative atomic mass

Answer 2

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

Question 3

molar mass

Answer 3

mass in grams of 1 mole of a substance and is given the unit g/mol

Question 4

amount formula

Answer 4

mass / molar mass

Question 5

gas volume

Answer 5

amount x 24

Question 6

concentration

Answer 6

amount / volume

Question 7

cm^3 to dm^3

Answer 7

divide by 1000

Question 8

cm^3 to m^3

Answer 8

divide by 1,000,000

Question 9

dm^3 to m^3

Answer 9

divide by 1000

Question 10

% mass

Answer 10

mass of chemical / total mass of compund x100

Question 11

Avogadro’s constant

Answer 11

6.02 x 10^23

Question 12

no. of particles

Answer 12

amount of substance x Avogadro’s constant

Question 13

density

Answer 13

mass / volume

Question 14

empirical formula

Answer 14

simplest ratio of atoms of each element in the compound

Question 15

method for finding empirical formula

Answer 15

1. divide each mass by the atomic mass of the element
2. divide by the smallest one of the number
3. may need to multiply to get a whole number

Question 16

molecular formula

Answer 16

actual number of atoms of each element in the compound

Question 17

making a solution

Question 18

diluting a solution

Question 19

new diluted concentration

Answer 19

original conc x
original vol/new diluted vol

cAvA = cBvB

Question 20

ideal gas equation

Answer 20

pV = nRT

p - pressure - Pa
V - volume - m^3
T - temperature - K
n - moles

Question 21

using a gas syringe

Question 22

reacting volumes of gas

Answer 22

equal volumes of any gases measured under the same conditions of temperature and pressure contain equal numbers of molecules

Question 23

molar volume

Answer 23

volume occupied by 1 mole of any gas

Question 24

titration procedure

Answer 24

• rinse equipment
• pipette 25cm^3 of alkali into conical flask
• touch surface of alkali with pipette
• add acid solution from burette
• make sure the jet space is filled with acid
• add a few drops of indicator
• observe colour change for the indicator used
• use a white tile underneath the flask to help observe the colour change
• add acid to alkali while swirling mixture and add acid drop-wise at end point
• note burette reading before and after addition of acid
• repeats titration until at least 2 concordant results are obtained

Question 25

safety precautions

Answer 25

- acids and alkalis are corrosive (at low concentration acids are irritant) - wear eye protection and gloves

Question 26

colour change phenolphthalein

Answer 26

pink to colourless end point - no colour

Question 27

colour change methyl orange

Answer 27

yellow to red end point - orange

Question 28

measurements

Answer 28

values taken as the difference between the judgements of two values

Question 28

readings

Answer 28

values found from a single judgement when using a piece of equipment

Question 29

% uncertainty

Answer 29

uncertainty / measurement made on apparatus x 100

Question 30

% yield

Answer 30

actual / theorotical x 100

Question 31

percentage atom economy

Answer 31

mass of useful products / mass of all reactants x 100

Question 32

how is salt formed

Answer 32

when the H+ ion of an acid is replaced by a metal ion or an ammonium ion

Question 33

metal displacement reactions

Answer 33

more reactive metals will displace less reactive metals from their compounds

Question 34

halogen displacement reactions

Answer 34

a halogen that is a strong oxidising agent will displace a halogen that has a lower oxidising power from one of its compounds

Question 35

precipitation reactions

Answer 35

insoluble salts can be made by mixing appropriate solutions of ions so that a precipitate is formed

Question 36

hazard

Answer 36

a substance or procedure that has the potential to do harm

Question 37

e.g. of hazards

Answer 37

toxic flammable harmful irritant corrosive oxidising carcinogenic

Question 38

risk

Answer 38

probability or chance that harm will result from the use of a hazardous substance or a procedure

Question 39

minimising risk - irritant

Answer 39

dilute acids and alkalis wear goggles

Question 40

minimising risk - corrosive

Answer 40

stronger acids and alkalis - wear goggles

Question 41

minimising risk - flammable

Answer 41

keep away from naked flames

Question 42

minimising risk - toxic

Answer 42

wear gloves avoid contact with skin wash hands after use

Question 43

minimising risk - oxidising

Answer 43

keep away from flammable materials

Question 44

safety dealing with excess acid

Answer 44

Sodium hydrogen carbonate (NaHCO3) and calcium carbonate (CaCO3) are good for neutralizing excess acid if acid spills because they are not corrosive and will not cause a hazard if used in excess. They have no toxicity