Flashcards in Unit 8-Chemical analysis Deck (59):
If a substance is chemically pure will it melt or boil at a specific temperature?
How can you test the purity of a sample?
By measuring its melting or boiling point and comparing it to the melting and boiling point of the pure substance.
The closer your measured value is to the actual melting point or boiling point...
The purer your sample is.
What does it mean if there are impurities in your sample?
It will have a lower boiling point and it will increase the melting range of your substance.
What are formulations?
They are useful mixtures with a precise purpose that are made by following a formula. Each component contributes to the properties of it so that means it is a required function.
What does a pure substance mean?
A substance that hasn't had anything added to it so it's in it's natural state.
What are formulations really important for?
The pharmaceutical industry.
Give two examples of where formulations can be found.
What are the two phases in chromatography?
-The mobile phase.
-The stationary phase.
What is the mobile phase?
Where the molecules can move.
What does the mobile phase always happen with?
Liquids and gases.
What is the stationary phase?
Where the molecules can't move.
What does the stationary phase happen with?
Solids and some thick liquids.
What is chromatography?
An analytical method used to separate the substances in a mixture which helps you to identify the substances.
In chromatography what is formed between the two phases?
Why is an equilibrium formed between the two phases?
Because the substances in the sample constantly move between the two phases.
What does the amount of time molecules spend in each phase depend on?
-How soluble they are in the solvent.
-How attracted they are to the paper.
How will a pure substance behave in chromatography?
It will only ever form one spot because there is only one substance in the sample.
What type of molecule will spend longer in the stationary phase?
Molecules with high solubility in the solvent and which are less attracted to the paper.
If a molecule spends longer in the mobile phase what does this mean?
It will travel further up the paper.
What is the result of chromatography?
What is an Rf value?
The ratio between the distance travelled by the dissolved substance (the solute) and the distance travelled by the solvent.
What is the equation for the Rf value in chromatography?
Rf= distance travelled by substance divided by distance travelled by solvent.
How do you test for chlorine?
Using litmus paper.
What will happen to the litmus paper when testing for chlorine?
It will bleach it.
What test do you use to test for oxygen?
The splint test.
How do you do the splint test?
Put a glowing splint inside a test tube containing oxygen.
How do you know if there is oxygen present in the splint test?
The oxygen will relight the glowing splint.
What test do you use to test for carbon dioxide?
The cloudy limewater test.
How do you do the cloudy limewater test?
Bubble carbon dioxide through an aqueous solution of calcium hydroxide (limewater).
What is limewater also known as?
How will you know if there's carbon dioxide present in the limewater test?
The solution will turn cloudy.
What test do you use to test for hydrogen?
The squeaky pop test.
How do you do the squeaky pop test?
Hold a lit splint at the open end of a test tube containing hydrogen.
How will you know if there is hydrogen present in the squeaky pop test?
It will made a squeaky pop.
What for common gases can you test for easily?
How do you test for sulfate ions?
Use a dropping pipette to add a couple of drops of dilute hydrochloric acid followed by a couple drops of barium chloride solution t your mystery solution.
Why is hydrochloric added in the test for sulfate ions?
To get rid of any traces of carbonate ions before you do the test because they would produce a precipitate and confuse the results.
How do you test for a halide ion?
Add a couple of drops of dilute nitric acid followed by a few drops of silver nitrate solution to your mystery solution.
What precipitate does a chloride produce in the halide test?
A white precipitate of silver chloride.
What precipitate does a bromide produce in a halide test?
A cream precipitate of silver bromide.
What pecipitate does an iodide produce in a halide test?
A yellow precipitate of silver iodide.
How can you test for various metal ions?
By heating your substance and seeing whether it burns with a distinctive colour flame.
What colour will the flame look with lithium ions?
What colour will the flame look with sodium ions?
What colour will the flame look with potassium ions?
What colour will the flame look with calcium ions?
What colour will the flame look with copper ions?
What are two disadvantages to the flame test for metal ions?
-The flame colours of some ions may be hidden by the colour of others.
-Some people may not be able to tell the difference between crimson and red/orange.
How do you carry out the practical for metal ions?
1)Clean a platinum wire loop in dilute HCL.
2)Hold it in a blue flame until it burns without colour.
3)Dip the loop in the sample.
4)Put it back in the flame to see the colour.
What is flame emission spectroscopy?
When a sample is placed in a flame and the light passes through a spectroscope.
What can a spectroscope do?
Detect wavelengths of light to produce a line spectrum.
What does the combination of wavelengths emitted depend on?(flame emission spectroscopy)
The charge and it's electron arrangement.
What does the intensity of the spectrum in fame emission spectroscopy indicate?
The concentration of the ion in the solution.
What can line spectrums be used for?
Why does flame emission spectroscopy work?
As the ions heat up their electrons become excited.When the electrons drop back to their original energy levels,they transfer energy as light.
Does flame emission spectroscopy work for mixtures?
With mixtures what is more useful ...flame emission spectroscopy or flame tests?
Flame emission spectroscopy.