Mixtures Flashcards
What is the state symbol for a solid?
(s)
What is the state symbol for a gas?
(g)
What is the state symbol for a liquid?
(l)
What is the state symbol for an soluble substance in water or aqueous?
(aq)
When is a substance aqueous?
When the substance is soluble in water and water is present in the reaction
Give the types of salt which are always soluble
All nitrate salts are soluble
All sodium, potassium (group 1) or ammonium salts are soluble
State the solubility rule for halides
All Halides are soluble except for lead and silver
State the solubility rule for sulfates
All sulfates are soluble except for lead and barium
Which of the following salts are soluble?
Na2CO3 BaSO4 Mg(NO3)2 PbCl2
Na2CO3 Mg(NO3)2 are soluble
BaSO4PbCl2 are insoluble
All sodium salts are soluble
All nitrate salts are soluble
All sulfate salts are soluble except for Barium
All halide salts are soluble except for lead
State the solubility rules for oxides, hydroxides and carbonates
All oxide, hydroxides and carbonates are insoluble except for sodium, potassium or ammonium
Outline the method for chromatography
- draw a pencil line at the bottom of the paper using a ruler
- create dots of ink along the pencil line
- curl the paper into a cylinder (with the pencil line at the bottom) and fasten with a paper clip at the top
- add a small amount of water to a beaker
- stand the cylinder with the pencil line at the bottom in the baker making sure the water level is below the pencil line
- leave until the solvent front approaches the top of the paper- remove the chromatogram
- mark the solvent front and leave to dry
What is the pencil line called on a chromatogram?
The base line
When carrying out chromatography, why must the water level be below the pencil line (base line)?
Otherwise the ink samples would dissolve into the water and would not travel up the paper. You want the water to move up the paper- taking the ink with it.
What is the formula for finding the Rf value of an pigment in chromatography?
Rf= distance pigment moved from base line / distance solvent moved from base line
Remember your Rf values will always be less than 1.
You are using a ruler so you must measure to a mm. It is best to record the distance in mm to avoid any mistakes.
When carrying out chromatography on a sample of inks, what does it mean if the ink does not move from the base line?
That particular ink is insoluble in that solvent
When Alex carried out chromatography, none of his ink samples moved from the base line. What could Alex do to get the ink to move from the base line so that he can compare the ink samples?
The ink samples are not soluble in that solvent. Alex should change the solvent.
Amelie noticed that one sample of ink did not separate into different spots as it travelled up the chromatography paper, but it stayed as one spot. What can Amelie conclude about that sample of ink?
That sample of ink is soluble in water but is a pure sample with only one pigment. It is not a mixture of two pigments.
Amelia noticed that one sample of ink separated into two different spots as it travelled up the chromatography paper, with one dot travelling further than the other. What can Amelia conclude about that sample of ink?
That sample of ink is soluble in water but is a mixture of two pigments. It is not pure, not one pigment.
Note: One pigment is more soluble than the other and travels further up the paper.
In chromatography, what is the relationship between solubility of a pigment and its Rf value?
The more soluble a pigment is the further it travels up the paper, the larger the Rf value.
note: an Rf value can never be larger than 1
What doe the symbol Rf stand for?
Retardation factor