C3/Quantitive Chemistry

Question 1

what is the law of conservation of mass?

Answer 1

no atoms are made or lost during a chemical reaction. the mass of the products equals the mass of the reactions.

Question 2

how do you calculate the relative formula mass of a compound?

Answer 2

add up all the RFM’s of all the atoms in the compound

Question 3

why can it appear for mass to be lost in a chemical reaction?

Answer 3

a gas is produced and the mass of the gas isn’t taken into account

Question 4

what is the symbol of a mole?

Answer 4

mol

Question 5

what unit of mass is used to measure the amount of a substance needed to make one mole?

Answer 5

grams

Question 6

how many grams of sodium are needed for 1 mole of sodium?

Answer 6

11g (relative atomic mass of sodium is 11)

Question 7

why is it common to use one reactant in excess?

Answer 7

so the other reactant becomes the limiting factor

Question 8

what unit is concentration of solutions measured in?

Answer 8

g/dm3 or grams/decimetre

Question 9

how many cm3 are in 1dm3?

Answer 9

1000

Question 10

what is the mathematical formula for calculating the concentration of a solution?

Answer 10

concentration=mass/volume

Question 11

give 3 reasons why you never get 100% atom economy in a chemical reaction

Answer 11

reaction may not go to completion because it’s reversible
some of the product may be lost when it’s separated from the reaction mixture
some of the reactants may react in different to the expected reaction

Question 12

what is the mathematical formula to calculate percentage yield?

Answer 12

%yield= mass of actually made product/maximum theoretically mass of produxt X100

Question 13

what is the mathematical formula for atom economy?

Answer 13

relative formula mass of desired product from equation/sum relative formula masses of all reactants from equation X100