Chemical Analysis

Question 1

what is a pure substance

Answer 1

only one element or compound

Question 2

how can you test that a substance is pure

Answer 2

test melting point. An impurity will higher or lower melting point and increase boiling range

Question 3

what are formulations with examples

Answer 3

useful mixtures with a precised purpose

paint
solvents
binders
fuels
cosmetics 
fertilizers 
metal alloys

Question 4

why are formulations useful for medicines

Answer 4

so goes to the right party of the body at the right concentration and has the right shelf life

Question 5

what is the mobile phase of chromatography

Answer 5

the solvent that moves through the paper

Question 6

what is the stationary phase of chromatography

Answer 6

its the paper. so the mobile phase moves through the stationary phase and carry s anything dissolved in it

Question 7

what determines how long a solute will stay in the mobile stage of chromatography

Answer 7

how soluble they are

how attracted they are to the paper

Question 8

what is the Rf value

Answer 8

distance traveled by the substance / distance traveled by the solvent

Question 9

test for chlorine

Answer 9

turns damp litmus paper white

Question 10

test for oxygen

Answer 10

relights glowing splint

Question 11

test for hydrogen

Answer 11

squeaky pop by lit splint

Question 12

test for carbon dioxide

Answer 12

turns lime water cloudy

cloudiness is calcium carbonate

Question 13

flame test for metal ions

Answer 13

lithium - crimson
potassium - lilac
calcium - orange 
copper - green 
sodium - yellow

Question 14

precipitation formed when sodium hydroxide is added to metal ions

Answer 14

calcium - white
copper -  blue
iron II - green
iron III - brown
aluminum - white to colourless
magnesium -  white

Question 15

how would you test for carbonate ions (negative)

Answer 15

add an acid to solution and it will fizzle. Bubble the gas through the lime water. Should turn cloudy

Question 16

how do you test for halide ions (negative)

Answer 16

add nitric acid followed by silver nitrate solution

chloride - white precipitate
bromide - cream
iodide - yellow

Question 17

how do you test for sulfate ions (negative)

Answer 17

add HCI and then barium chloride solution

white precipitate

Question 18

why do you add HCI when testing for sulfate ions

Answer 18

to react any carbonate ions which would also produce a white precipitate when reacted with barium chloride

Question 19

how does flame emission spectroscopy work

Answer 19

sample is placed in a flame. Electrons get exited and move up an energy level. When they drop back down they transfer energy as light. This light is passed through a spectroscope which can defer different wavelengths of light to produce a line spectrum. Different ions emit different wavelengths of light so will produce a different line spectrum.

Question 20

how can you tell the concentration of the ion in a solution using a line spectrum

Answer 20

the intensity of spectrum

Question 21

advantages of flame emission spectroscopy

Answer 21

very sensitive
very fast
very accurate