C2.1

Question 1

empirical formula

Answer 1

simplest whole number ratio of atoms of each element in a compound e.g C6H6= CH

Question 2

describe a pure element

Answer 2

a pure element or compound contains only one substance

Question 3

describe an impure element or compound

Answer 3

impure materials may be composed of a mixture of elements, compounds or both

Question 4

filtration

Answer 4

separates an insoluble solid from a liquid

Question 5

soluble

Answer 5

substance that can dissolve

Question 6

insolube

Answer 6

substance that can’t dissolve

Question 7

crystillisation

Answer 7

used to separate a soluble solid from a liquid

Question 8

chromatography

Answer 8

used to separate mixtures

Question 9

stationary phase

Answer 9

the paper

Question 10

mobile phase

Answer 10

the solvent

Question 11

establishing purity

Answer 11

-purity of an element can be established by it’s melting point
-impure compounds have a large range of melting points
-pure compounds have a definite melting and boiling point

Question 12

solute

Answer 12

soluble solid

Question 13

solvent

Answer 13

liquid

Question 14

solute + solvent –>

Answer 14

solute + solvent –> solution

Question 15

why does distillation work?

Answer 15

distillation works because parts of the mixture have different boiling points, the mixture is heated and the substance with the lowest boiling point evaporates first, it enters the condenser where it’s cooled, condensed and collected

Question 16

fractional distillation

Answer 16

-used to separate a mixture of two or more misicrite liquids
-fractioning column improves separation as it has a high surface area

Question 17

how does chromatography work?

Answer 17

each substance travels at a different rate, depending on their relative attractions to each phase

Question 18

why do we draw the start line in pencil for chromatography?

Answer 18

if we drew it in pen it would bleed into the other colours

Question 19

why should the water be below the start line in chromatography?

Answer 19

the water would touch the dyes and dissolve them of the paper

Question 20

how do we calculate RF value?

Answer 20

distance travelled by substance / distance travelled by solvent

Question 21

thin layer chromatography

Answer 21

more accurate from of chromatography and uses an inert layer for the stationary phase