tech

Question 1

types of separation techs

Answer 1

• filtration
  -evaporation to dryness
• crystallisation
• simple distillation
• magnetic attraction
• sublimation
• filtration
• separating funnel

Question 2

when to use filtration

Answer 2

separate insoluble solid from liquid
example: chalk water, tea leaves from tea

Question 3

process filtration

Answer 3

use filter paper
liquid will be FILTRATE
solid will be RESIDUE

Question 3

when to use evaporation to dryness

Answer 3

dissolved liquid form solution (production of salt in salt mine)

when solubility of salt doesnt change significantly w temp ( dont use crystallisation)

Question 3

process evaporation to dryness

Answer 3

heat solution in evaporating dish, evaporate off all substance

Question 3

when to use crystallisation

Answer 3

obtain dissolved solid from solution as pure crystals (copper 2 sulfate solution)

Question 4

process crystallisation

Answer 4

• heat in evaporating dish, evaporate MOST of solvent
• solution will be SATURATED
• allow solution to COOL, crystals will form
• filter mixture to get crystals as residue
• dry crystals btwn filter paper

Question 5

diff btwn crystallisation and evaporation to dryness

Answer 5

• ETP solids may not be pure,may decompose (sugar eg)
• Impurities will not cyrstallies out during Crystallisation
• ETP evaporates all the solvent, crystallisation evaporates most of the solvent

Question 6

when to use simple distillation

Answer 6

obtain pure liquid from solution ( seawater, sodium chloride solution, sugar solution)

Question 7

process for distillation

Answer 7

heat solution till it turns into vapour n goes into condenser, let it condense into liquid, pure liquid will be distillate, residue remain in flask

Question 8

What are boiling chips for?

Answer 8

Ensure smooth boiling process

Question 9

Why is thermometer bulb placed beside arm leading to condenser

Answer 9

Measure temp of water vapour, tell boiling point of liquid

Question 10

What is the use of water entering from below

Answer 10

Ensure complete condensation of water vapour passing through condenser

Question 11

whats sublimation

Answer 11

solid changing to gas without going through liquid by heating (iodine from sand, ammonium chloride from sodium chloride)

Question 12

process sublimation

Answer 12

mixture of solids heat in evaporating dish, solid that sublimes turn into vapour, condenses back to solid on funnel, become pure solid called sublimate. other solid is residue

Question 13

whats paper chromatography

Answer 13

to separate subs that are soluble in a common solvent

Question 14

why does the start line need to be drawn in pencil

Answer 14

ensure ink doesnt dissolve in the solvent used and interfere with separation of mixture

Question 15

why does the paper used need to be long

Answer 15

ensure complete separation of mixture into its components

Question 16

can start line be below solvent level? why?

Answer 16

no. if it is below solvent level, it would be dissolved into the solvent before it can be separated into its components

Question 16

how to calculate Rf value

Answer 16

dist move by subs / dist moved by solvent