C8 Chemical Analysis

Question 1

how to test how pure a substance is:

Answer 1

1) measure is melting and boiling point and compare it to the melting and boiling point of the pure substance (you can find it in a data book)
2) the closer your measured value is to the actual melting and boiling point, the purer it is.

Question 2

what will impurities do in the sample:

Answer 2

lower the melting point and increase the melting range of the substance

increase boiling point and increase range of temperatures that the sample boils for.

Question 3

pigment in paint

Answer 3

gives the paint colour

Question 4

solvent in paint

Answer 4

used to dissolve the other components and alter the viscosity

Question 5

binder (resin) in paint

Answer 5

forms a film that holds the pigment in place after its been painted on

Question 6

additives in paint

Answer 6

added to further change the physical and chemical properties of the paint

Question 7

why are formulations import in the pharmaceutical industry

Answer 7

for example by altering the formulation of a pill chemists can make sure it delivers the drug to the correct part of the body at the right concentration that its consumable and has a long enough self life.

Question 8

how to test for chlorine:

Answer 8

chlorine bleaches damp litmus paper turning it white.

if you use blue litmus paper it may turn red for a moment because its acidic

Question 9

how to test for oxygen:

Answer 9

if you pit a glowing splint inside a test tube containing oxygen, the oxygen will relight the glowing splint.

Question 10

how to test for carbon dioxide:

Answer 10

bubbling carbon dioxide through (or shaking carbon dioxide with) a aqueous solution of calcium hydroxide (lime water) causes the solution to turn cloudy

Question 11

how to test for hydrogen:

Answer 11

if you hold a burning splint at the open end of a test tube containing hydrogen you get a squeaky pop.

the noise comes from the hydrogen burring quickly in the oxygen in the air to form water.

Question 12

the moble phase

Answer 12

where molecules can move. this is always a liquid or gas

Question 13

the stationary phase

Answer 13

where the molecules cant move. this can be a solid or a really thick liquid

Question 14

paper chromatography:

Answer 14

1) the substances constantly move between the mobile and the stationary phases - an equilibrium is formed between the two phases

2) the mobile phase moves through the stationary phase and anything dissolved in the mobile phase moves with it.

3) how quickly a chemical moves depends on how its distributed between the two phases - more time in stationary or more time in mobile

4) the chemicals that spend more time in the mobile phase will move further through the stationary phase

5) the components in a mixture will normally separate through the stationary phase, so a long as all the components spend different amounts of time in the mobile phase

6) the separated components form spots. the number of sport formed may change in different solvents a the distribution of the chemical will change depending on the solvent

7) a pure substance will only ever form one sport in any solvent, since there is only one substance in the sample

Question 15

the stationary phase is often

Answer 15

chromatograpohy paper

Question 16

the mobile phase is often

Answer 16

the solvent ed ethanol or water

Question 17

the amount of time the molecules spend in each phase depends on two things:

Answer 17

how soluble they are in the solvent
how attracted they are to the paper

molecules with a higher solubility in the solvent which are less attracted to the paper will spend more time in the mobile phase and they will be carried further up the paper

Question 18

forumla for R1 vaule

Answer 18

R1 = distance travelled by substance / distance travelled by solvent