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GCSE6 Analysis

AQA GCSE chapter 12 chemical analysis

QuestionAnswer
Describe how to carry out a chromatography experiment draw a start line in PENCIL, ABOVE the water level; place a dot of your mixture and a dot for references on start line; place the paper in beaker WITH A LID; remove paper before the solvent reaches the top of the paper; draw a line on the solvent FRONT
Why does the start line need to be drawn in PENCIL? if the line was drawn in ink, the ink could rise with the solvent as well as your mixture
Why does the start line need to be drawn ABOVE the water level? If the line was below, the dot from the mixture would dissolve into the water instead of rising up the paper
Why do we place a lid on top of the beaker? to prevent teh solvent from evaporating
Looking at a chromatogram, how would you know if a chemical is a mixture? There would be more than one dot above the start line
Looking at a chromatogram, how would you know if HOW MANY different chemicals were in a mixture? COUNT the dots above the start line
Looking at a chromatogram, how would you know if how many different chemicals were in a mixture? COMPARE the HEIGHT of the dots above the start line of the mixture to the HEIGHT of reference/pure chemicals; if two dots are at the same height, then they are the same chemical
Looking at a chromatogram, how would you know which chemical is the most soluble? the most soluble chemical rises the furthest; has the biggest Rf
Explain why a chemical rise up the paper A chemical rises up the paper when it forms STRONGER bond with the mobile phase (solvent) than the bond it forms with the stationary phase (paper)
What is the stationary phase? the paper
What is the mobile phase? the solvent
How do you work out the Rf for a given dot? measure the distance from the start line to the MIDDLE of the dot; measure the distance from the start line to the solvent front; divide the start-to-dot by start-to-front
Looking at a chromatogram, how would you know if how many different chemicals were in a mixture? COMPARE the Rf of the dots above the start line of the mixture to the Rf of reference/pure chemicals; if two dots are at the same Rf, then they are the same chemical
What is the chemical test for oxygen gas? A GLOWING splint RELIGHTS
What is the chemical test for hydrogen gas? A LIT splint makes a SQUEAKY pop
What is the chemical test for carbon dioxide gas? when BUBBLED through LIMEWATER, the limewater turns cloudy
(CHALLENGE) why is it not enough to identify carbon dioxide gas to say “carbon dioxide turns off a flame”? Because nitrogen gas also turns off a flame
What is the chemical test for Al+3? a white precipitate forms with sodium hydroxide; the precipitate WILL dissolve if more Sodium Hydroxide is added
What are the 2 chemical tests for Ca+2? a white precipitate forms with sodium hydroxide; the precipitate WILL NOT dissolve if more Sodium Hydroxide is added
What are the 2 chemical tests for Cu+2? A blue precipitate forms with sodium hydroxide; also green flame
What is the chemical test for Fe+2? A green precipitate forms with sodium hydroxide solution
What is the chemical test for Fe+3? A brown precipitate forms with sodium hydroxide solution
What is the chemical test for NH4+? A white precipitate forms with sodium hydroxide solution; if the precipitate is heated, a pungent gas that turns red litmus paper to blue is given off; the gas is Ammonia
What is the chemical test for Cl-? A white precipitate forms with silver nitrate and acid solution
What is the chemical test for Br-? A cream precipitate forms with silver nitrate and acid solution
What is the chemical test for I-? A yellow precipitate forms with silver nitrate and acid solution
Describe a simple chemical test to distinguish between Cl- and I- ions? Add acid and then silver nitrate solution; a white precipitate indicates Cl- ions and a yellow precipitate indicates I- ions
Describe a simple chemical test to distinguish between Fe+2 and Fe+3 ions? Add Sodium Hydroxide; if the precipitate that forms is green, then the ion is Fe+2; if the precipitate is brown, then Fe+3
What is the colour of the flame when you burn Na+ ions? Yellow
What is the colour of the flame when you burn Ca+2 ions? brick red (orange-red)
What is the colour of the flame when you burn Cu+2 ions? Green
What is the colour of the flame when you burn K+ ions? Lilac
What is the colour of the flame when you burn Li+ ions? Crimson
What is the chemical test for CO3-2? Fizz on addition of HCl; the gas will turn limewater cloudy
What is the chemical test for SO4-2? A white precipitates forms on addition of dil HCl and BaCl2(aq)
A sample of water produces a green precipitate on addition of Sodium Hydroxide and fizzes on addition of acid. What ions are present in solution? Fe+3 and CO3 -2
Give two applications to flame tests and chemicals tests Blood tests and testing for water
A sample of water produces a blue precipitate on addition of Sodium Hydroxide and a cream precipitate on addition of Nitric acid + silver nitrate. What ions are present in solution? Copper Cu+2 and Bromide Br-1 ions
(HIGHER) What is the IONIC equation for the precipitation of copper hydroxide? Place the ions as reactants: Cu+2 + OH- --> ....; Work out formula of copper hydroxide: Cu(OH)2; The copper hydroxide is the product, after the arrow; Cu+2 + OH- --> Cu(OH)2; Balance: Cu+2 + 2 OH- --> Cu(OH)2
(HIGHER) What is the IONIC equation for the precipitation of silver bromide? Place the ions as reactants: Ag+ + Cl-  ...; Work out formula of silver bromide: AgBr; The silver bromide is the product, after the arrow: Ag+ + Cl-  AgBr; check Balancing
(HIGHER) What is the IONIC equation for the reaction between Sodium Hydroxide and copper ions? Always look for spectator ions: classical spectators are sodium, potassium and nitrate ions. Then write the ionic equation as usual.
(HIGHER) What is the IONIC equation for the reaction between Sodium Hydroxide and copper sulfate? WORD : Sodium Hydroxide(aq) + Copper Sulfate(aq) --> Sodium Sulfate(aq)+Copper Hydroxide(s); CHECK FORMULAE NaOH + Cu(SO4) -> Cu(OH)2 + Na2(SO4); BALANCE 2NaOH + Cu(SO4) -> Cu(OH)2 + Na2(SO4); remove ions that stay (aq): 2OH(aq) + Cu(aq) -> Cu(OH)2(s)
(HIGHER) What is the IONIC equation for the reaction between Silver Nitrate and Sodium Chloride? WORD : Silver Nitrate+Sodium Chloride --> Sodium Chloride(aq) + Silver Chloride(s); CHECK FORMULAE Ag(NO3)(aq) + NaCl (aq)->AgCl(aq) + Na(NO3)(aq); remove ions that stay (aq) AND CHECK CHARGES: Ag+(aq) + Cl-(aq) --> AgCl(s)
Created by: ursulinechem2