C5-chemical analysis

Question 1

how to decide what chemical to use.

Answer 1

-the amount of impurities.
-what the impurities.
-how they can affect the process.
-whether they’ll end up in the product and if it matters.

Question 2

what is a titration?

Answer 2

measures the volume of alkali that it can neutralise.

Question 3

what is chromatography used for?

Answer 3

-separate and identify chemicals in a mixture.
-check the purity of a chemical.
-purify small samples of a chemical.

Question 4

chromatography phases.

Answer 4

-chemical moves quickly if the position of equilibrium favours the mobile phase.
-chemical moves slowly if it favours the stationary phase.

Question 5

how to work out the retardation factor?

Answer 5

distance moved by chemical
——————————————
distance moved by solvent

Question 6

what is filtration?

Answer 6

-a quick and easy way of separating a liquid, solution or gas from a solid.
-the solid or residue is caught by the filter while the liquid filtrates.
-in order to obtain a pure sample may need to repeat several times.

Question 7

what is crystallisation?

Answer 7

-crystals a formed by evaporating the water from a solution of a salt.
-size relates to the rate of evaporation of the water.
slowly = larger
-different color indicate impurities.

Question 8

what is distillation?

Answer 8

-purifies a solution by heating and cooling.
-separates mixture of liquids by their boiling points.

Question 9

what is fractional distillation?

Answer 9

-a process which multiple simple distillation can be carried out in a single piece of apparatus.
-larger the distance in bpts, the easier it is to collect a pure sample.

Question 10

what is a qualitative method?

Answer 10

-used if the aim is to find out which chemicals are present in a material.
-chemical composition.

Question 11

what is a quantitive method?

Answer 11

-used if the aim is to find out how much of each chemical is present.

Question 12

what is the purpose of a flame test?

Answer 12

used to identify metal ions on a salt.

Question 13

flame test results.

Answer 13

-sodium, bright yellow
-potassium, lilac
-calcium, orange-red
-copper, blue-green

Question 14

another method of identifying ions other than a flame test.

Answer 14

-precipitate reactions.
-2 solutions are mixed and a solid forms.
-can identify both metals and non-metal ions.
-relies on different solubilities.

Question 15

soluble or insoluble.

Answer 15

nitrates - soluble
salts of sodium and potassium - soluble
silver chloride - insoluble
silver bromide - insoluble
calcium carbonate - insoluble
hydroxide of metals not in group 1 - insoluble.

Question 16

precipitate colours.

Answer 16

copper - light blue
iron - green
iron 3+ - red brown
calcium - white
zinc - white (only soluble one)

Question 17

chloride, bromide, iodine + silver ions

Answer 17

insoluble precipitate

Question 18

sulfate ions + barium ions

Answer 18

white precipitate

Question 19

carbonate ions + dilute acid

Answer 19

carbon dioxide

Question 20

what is an emission spectrometer?

Answer 20

-analyses the spectrum of light that is emitted from a hot sample.
-checks the purity.
-sensitive, accurate, faster
-costly

Question 21

what is the conservation of mass?

Answer 21

the total mass stays constant.

Question 22

what’s the avrogardo constant?

Answer 22

6x10(23)

Question 23

how to work out the mass of a substance?

Answer 23

number of moles x mr

Question 24

how to work out percentage yield?

Answer 24

actual yield
———————- x100
rhetorical yield

Question 25

what is the molar volume of gases?

Answer 25

-24dm(3)
-1dm(3) = 1000cm(3)

Question 26

how to work out the volume (dm3)?

Answer 26

number of moles x molar volume (24dm3)

Question 27

how to work out the concentration (g/dm3)?

Answer 27

mass (g)
———————
volume (dm3)

Question 28

how to work out the concentration (mol/dm3)?

Answer 28

number of moles
—————————
volume (dm3)

Question 29

what does a acid and alkali make?

Answer 29

salt + water