Amount of chemical substance

Question 1

what are the units for ram

Answer 1

grams / mole

Question 2

what is an expression for ram

Answer 2

mass / no. of moles

Question 3

in addition or subtraction what should you report your answer to

Answer 3

the least no. of decimal places in the question

Question 4

in multiplication or division what should you report your answer to

Answer 4

the least number of significant figures in the question

Question 5

what is an atom

Answer 5

a simple particle consisting of a nucleus with protons and the same no. of electrons

Question 6

what is a molecule

Answer 6

groups of atoms held together by covalent bonds

Question 7

what is an ion

Answer 7

a charged particle

Question 8

ionic equation of acid + hydroxide

Answer 8

H+ (aq) + OH- (aq) -> H2O (l)

Question 9

ionic equation of acid + carbonate

Answer 9

2H+ (aq) + CO32- (aq) -> H2O (l) + CO2 (g)

Question 10

ionic equation of acid + hydrogencarbonate

Answer 10

H+ (aq) + HCO3- (aq) -> H2O (l) + CO2 (g)

Question 11

ionic equation of acid + ammonia

Answer 11

H+ (aq) + NH3 (aq) -> NH4+ (aq)

Question 12

what is the solubility of group 1 and ammonium salts

Answer 12

all soluble

Question 13

what is the solubility of nitrates

Answer 13

all soluble

Question 14

what is the solubility of sulphates

Answer 14

all soluble except calcium, lead, and barium

Question 15

what is the solubility of chlorides

Answer 15

all soluble except silver and lead

Question 16

what is the solubility of carbonates and hydroxides

Answer 16

insoluble except group 1 and ammonium salts

Question 17

what is relative atomic mass (ram)

Answer 17

the ratio of the average mass of one atom of an element compared to 1/12th the mass of one atom of carbon-12

Question 18

what is relative molecular mass (mr)

Answer 18

the ratio of the average mass of one molecule of an element or compound compared to 1/12th the mass of one atom of carbon-12

Question 19

how to calculate % by mass

Answer 19

% by mass = ar (Y) x number of atoms of Y in the formula / Mr (compound) x 100

Question 20

what does atom economy do

Answer 20

evaluate the efficiency of a reaction by showing how much of the products are converted into useful reactants

Question 21

how to calculate atom economy

Answer 21

% atom economy = mass of desired product / total mass of reactants x100

Question 22

what is avogadro’s number

Answer 22

6.023 x 10^23

Question 23

how many moles does 1 ram in grams of an element contain

Answer 23

1 mole

Question 24

how many moles does the mr in grams of a compound contain

Answer 24

1 mole

Question 25

equation for moles using mass and mr

Answer 25

n = m / mr

Question 26

how to calculate the no. of particles

Answer 26

no. of particles = no. of moles x avogadro's number

Question 27

what is the empirical formula

Answer 27

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

Question 28

molecular formula

Answer 28

this is the actual number of each element in a molecule. the molecular formula is a multiple of the empirical formula

Question 29

how to calculate empirical formula

Answer 29

1 - work out number of moles using mass / mr 2 - divide by the smallest number 3 - find the ratio

Question 30

what is a limiting reagent

Answer 30

the reactant that isn't in excess

Question 31

why do most reactants not have a 100% yield

Answer 31

- may have side reactions taking place - may lose product in purification - the conversion of reactant into product may not be complete - could be a reversible reaction

Question 32

how to calculate % yield

Answer 32

actual yield / theoretical max. yield x100

Question 33

how to calculate number of moles using concentration and volume and what units are used

Answer 33

n = c x v c - mol/dm^3 v - dm^3

Question 34

how to convert from concentration in mol/dm^3 to concentration in g/dm^3

Answer 34

conc. (g/dm^3) = conc. (mol/dm^3) / mr

Question 35

what is the ideal gas equation and what units are used

Answer 35

pV = nRT p - pressure (pa) v - volume (m^3) n - number of moles r - gas constant (8.31 j/mol/k) t - temperature (k)

Question 36

how to get from dm^3 to m^3 in volume

Answer 36

m^3 = dm^3 / 1000

Question 37

how to get from kPa to Pa in pressure

Answer 37

Pa = kPa x 1000

Question 38

how to get from degrees to kelvins in temperature

Answer 38

k = degrees + 273

Question 39

in reacting gas calculations what happens to volume when temp. and pressure are the same

Answer 39

volume becomes proportional to the no. of moles e.g H2O + 2O2 -> 2H2O if there was 10cm^3 of H2O used then there would be 20cm^3 of O2 due to balancing no.