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AQA GCSE Chapter 12

AQA GCSE Chapter 12 analysis DOUBLE ONLY

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
Created by: ursulinechem2