CHAPTER 10 CHEMICAL ANALYSIS Flashcards
What is a pure substance
A single element or a single compound and nothing else.
Whats special about the boiling and melting points of pure and unpure substances
Pure substances have a specific temperature whereas inpure have a range of temperatures
What is filtration used to separate,it’s equipment and how does it work
1.It separates insoluble solids from a liquid/solution
2.It has filter paper,funnel,residue,filtrate
3.A liquid/substance can pass through the microscopic holes in the filter called the filtrate where the solid or residue cannot so then its separated.
What is crystallisation used to separate,it’s equipment and how does it work
- Separates a soluble solids from a solution
2.Has a solution and a hot water bath
3.A mixture is heated gently until water evaporates which increases concentration of the solution until salt crystallises then all the water vaporises leaving behind salt crystals
What is simple distillation used to separate,it’s equipment and how does it work
1.Separates the solvent from the solution
2.Has a thermometer,2 gaps for water in and out, a condenser and the solution and solvent
3.Evaporated solute is collected through a condenser which cools the hot vapour until it condenses back into a liquid and can be collectee
Steps of chromatography RP(4)
1.Draw a straight base line in pencil using a ruler 1cm from bottom of paper. Use a ruler so you can accurately measure the distance travelled from the solvent accurately and we usr pencil so it doesn’t affect the ink in the experiment
- Place a small dot of dye from the capillary tube on the base line
- Then suspend the paper into the solvent making sure the base line is just above the water
4.Then measure the distance moved by the solvent and the distances moved by each colour from the starting line to the centre of the colour
Why may other samples move at different speed during chromatography
As it depends on the forces of attraction between the stationary and the ink and the mobile phase and the ink. If the stationary phase (the paper) had stronger forces of attraction with the ink it means that the ink moves slower. Whereas if the mobile phase (the water) had stronger forces of attraction with the ink it would move faster
How to find the Rf regarding chromatography
Rf = distance travelled by the sample / distance travelled by solvent(line to line)
What are the 4 tests for gases (which gas the test and observation if positive)
Hydrogen(H2) - Lighted splint - Squeaky pop
Oxygen(O2) - ‘glowing splint’ - relights
Chlorine(Cl2) - any damp indicator paper(red/blue litmus paper) - bleaches white
Carbon dioxide(CO2) - Bubble through limewater(calcium hydroxide solution) - turns milky white
