c8 - chemical analysis

Question 1

definition of pure substances

Answer 1

a single element or compund, not mixed with any other substance.

Question 2

properties of a pure substance

Answer 2

melt and boil at specific temperatures
e.g. pure water at 100C
unadultered
in its natural state

Question 3

define formulation

Answer 3

a mixture that has been designed as a useful

product

Question 4

how are formulations made?

Answer 4

are made by mixing the components in carefully measured quantities to ensure that the product has the required properties

Question 5

give examples of formulations

Answer 5

fuels
cleaning agents
paints
medicines
alloys
food

Question 6

what is chromatography

Answer 6

an analytical method used to seperate the substances in a mixture

Question 7

what are the two phases used in chromotogarphy

Answer 7

mobile phase - can move
e.g. liquid or gas
stationary phase - can’t move
e.g. solid or very thick liquid

Question 8

Rf value

the equation?

Answer 8

distance moved by substance/

distance moved by solvent

Question 9

how does Rf value change for different compounds in different solvents?

Answer 9

the compounds
in a mixture may separate into different spots depending on the solvent but a pure compound will produce a single spot in all solvents

Question 10

test for hydrogen

Answer 10

hold a lit splint at the open end of a test tube containing hydrogen
hydrogen burns rapidly with a squeaky pop sound

Question 11

test for oxygen

Answer 11

insert a glowing splint into the test tube of gas

the splint relights in oxygen

Question 12

test for chlorine gas

Answer 12

When damp litmus paper is

put into chlorine gas the litmus paper is bleached and turns white

Question 13

test for carbon dioxide

Answer 13

uses an aqueous solution of calcium hydroxide (lime water). When carbon dioxide is shaken with orbubbled through limewater the limewater turns milky (cloudy)