Paper 2 - Chemical Analysis Flashcards
How can we test for purities?
A chemically pure substance will =
Melt at a specific temperature
Boil at a specific temperature
How can we test for impurities?
An impurity will:
Have a lower melting point and increase melting range
Increase boiling point and increase boiling range
What is a formulation?
A formulation is a useful mixture with a precise purpose
What are examples of formulations?
Examples of formulations include :
Metal alloys, cleaning products, medicines, food
What is the stationary phase in chromatography?
In chromatography, the stationary phase is when the molecules can’t move
What is the mobile phase in chromatography?
The mobile phase in chromatography is when the molecules can move ( the solvent)
What is chromatography?
Chromatography is used to separate substances in a mixture
What is the process of chromatography?
Chromatography:
1) . The substances dissolve in mobile phase
2) . Mobile phase moves through stationery phase
3) . Substances that are more soluble in mobile phase or less attracted to stationary phase move futher
How can we test for hydrogen?
We can test for hydrogen when a lighted splint burns quickly with a pop (“squeaky pop test”)
How can we test for oxygen?
We can test for oxygen by relighting a glowing splint
How can we test for chlorine?
We can test for chlorine with litmus paper, where the litmus paper will turn white in chlorine gas
How can we test for carbon dioxide?
We can test for carbon dioxide when limewater turns cloudy in presence of CO2 gas
How can we test for carbonates?
Test for carbonates:
1) . Add a couple of drops of dilute acid
2) . Connect the test tube to a tube of lime water
3) . Carbonatic ions react to form CO2 which turns lime water cloudy
How can we test for halides? (BRINCLHOF elements)
We can test for halides by adding dilute nitric acid followed by silver nitrate solution to mystery solution
In the halide test, what will chloride show as?
Chloride has a white precipitate during the halide test
In the halide test, what will bromide show as?
Bromide will have a cream precipitate in the halide test
In the halide test, what will iodide show as?
Iodide will have a yellow precipitate in the halide test
What are the advantages of instrumental analysis? (flame emission spectroscopy)
The advantages of instrumental analysis are that it is sensitive (meaning it can detect tiny amounts), it’s fast and it’s accurate
What is flame emission spectroscopy?
Flame emission spectroscopy identifies ions in a solution (Each ion has a unique spectrum) and determines the concentration of ions
What colour will the lithium, sodium, potassium, calcium and copper flames appear as in flame tests for metal cations? (each)
Lithium = Red flame Sodium = Yellow flame Potassium = Purple flame Calcium = Orange flame Copper = Green flame
What is the symbol for a reversible reaction?
The symbol for a reversible reaction is ⇌ (two arrows pointing away from each other)
Complete the sentence: Equilibrium is reached when the forward and reverse reactions happen at exactly the same ____
rate
How do you find the rf value in chromatography?
You can find the rf value in chromatography by dividing the distance of the substance by the distance of the solvent
Plan out a chromatography experiment to investigate the colours in an ink
Chromatography experiment:
1) . put dots of known colours and ink on pencil line on chromatography paper
2) . place edge of the paper in water (the line is above the water )
3) . leave for the solvent to rise up through the paper
4) . when the solvent is near the top of the paper, remove and leave to dry
5) . compare positions of dots for known colours with that ink
Explain how paper chromatography separates the dyes in food colours (do not give details of how to do the experiment)
Paper chromatography separates dyes in food colouring as dyes move at different rates and different dyes have different solubilities
How can you tell there is more than one dye in an ink during a chromatography experiment?
You can tell there is more than one dye in an ink during a chromatography experiment as there will be more than one spot produced in a vertical column
How can you use chromatography to identify unknown dyes in food colouring?
You can use chromatography to identify unknown dyes in food colouring as you can compare the rf values and you can identify that the ones which move the same distance are the known dyes
