PAG 1 Moles determination

Question 1

outline procedure to find formula of a hydrated salt

Answer 1

weigh empty crucible
add hydrated salt to crucible and weigh crucible again
heat the crucible on tripod gently and then strongly
leave crucible to cool
weigh the crucible and anhydrous salt

Question 2

diagram for finding formula of a hydrated salt

Answer 2

Question 3

what assumptions are made when using this procedure to find the formula of a hydrated salt?

Answer 3

all the water has been lost
no further decomposition occurs

Question 4

all the water has been lost

Answer 4

difficult to tell if all the water has been lost

Question 5

what to do to ensure that all the water has been lost?

Answer 5

heat until constant mass
ensures all water has evaporated

Question 6

no further decomposition occurs

Answer 6

the anhydrous salt may decompose further due to over heating
further loss in mass

Question 7

how can you reduce the percentage error in mass calculations of anhydrous salts?

Answer 7

increase the mass of hydrated salt used
use a weighing scale with more decimal places

Question 8

outline how to identify an unknown metal

Answer 8

weigh sample of metal and add to conical flask
add a known conc of HCl to the conical flask
quickly replace the bung
measure the maximum volume of gas in the syringe

Question 9

diagram for identifying an unknown metal

Answer 9

Question 10

what improvements can be made to increase the accuracy in identifying an unknown metal?

Answer 10

heat until constant volume
all the gas to cool before measuring the volume