Topic 9 Flashcards
Why is the test for ions unique?
Each test is unique- it gives certain results depending on the ions present.
How can you test for a metal ion?
You can test for various metal ions by putting your substance in a flame and seeing what colour the flame goes.
What colour do Lithium ion (Li+) give when put in the flame?
Lithium ions give a red flame
What colour do Sodium ions (Na+) give when put in the flame?
Sodium ions give a yellow flame
What colour do Potassium ions (K+) give when put in the flame?
Potassium ions give a lilac flame
What colour do Calcium ions (Ca2+) give when put in the flame?
Calcium ions give an orange- red flame
What colour do copper ions (Cu2+) give when put in the flame?
Copper ions give a blue- green flame
Are metal hydroxides soluble or insoluble?
Many metal hydroxides are insoluble and precipitate out of solution when formed.
What do some hydroxides have?
Some hydroxides have a characteristic colour
Describe the test for metal hydroxides:
1) Add a few drops of sodium hydroxide to a solution of the mystery compound.
2) If a hydroxide precipitate forms, you can see it colour to tell which metal ion was in the compound
What is colour of precipitate of Aluminium ion?
White at first but then redissolves in excess NaOH to form a colourless solution.
What is colour of precipitate of Calcium ion?
White
What is colour of precipitate of Copper ion?
Blue
What is colour of precipitate of Iron (II)?
Green
What is colour of precipitate of Iron (III)?
Brown
What is the chemical test for ammonia ions?
1) To work out whether a substance contains ammonium ions(NH4+), all you need to do is add some sodium hydroxide solution to a solution of your mystery substance and gently heat it. If ammonia gas is given off, it means that there are ammonium ions in your mystery substance.
What is the chemical test for ammonia gas?
1) You can test for ammonia gas by holding a piece of damp red litmus paper over it. If the mystery gas is ammonia, it will turn blue.
Why is it not a good to smell the ammonia gas?
Ammonia has a distinctive smell and at high concentrations, ammonia is an irritant and toxic.
How can you test for carbonates using dilute acids?
1) To test for carbonates ions in solution add some dilute acid.
2) If there are carbonate ions present, the mixture will fizz- this is because the carbonate will react with the acid to produce carbon dioxide gas.
How can you test for carbon dioxide?
You can check to see if a gas is carbon dioxide by bubbling it through lime water. If it is carbon dioxide, the lime water turns milky.
How can you test for sulfate ions using barium chloride solution?
1) To test for sulfate ions in solution, first add some dilute hydrochloric acid to the test sample- this stops any precipitation reactions not involving sulfate ions from taking place.
2) Then add some barium chloride solution. If there are sulfate ions in the solution, a white precipitate of barium sulfate will form
How can you test for halide ions using silver nitrate solution?
To test for halide ions, add some dilute nitric acid followed by a few drops of silver nitrate solution.
What colour precipitate does chloride give ?
A chloride gives a white precipitate of silver chloride.
What colour precipitate does bromide give ?
A bromide gives a cream precipitate of silver bromide.
What colour precipitate does iodide give ?
An iodide gives a yellow precipitate of silver iodide.
What is flame photometry?
Flame photometry is an instrumental method that allows you to identity ions in a dilute solution.
What does each ion produce in a flame photometry?
Each ion produces a unique line spectrum with different lines present different places.
What does the intensity of the wavelength suggest?
The intensity of the measured wavelength indicates the concentration of that ion in solution.
How can you work out the concentration?
You can work the concentration from intensity using a calibration curve?
What can flame photometry be used for?
Flame photometry can also be used to identify different ions in mixtures.
Why is flame photometry more useful than flame test?
As flame test only work for substances that contain a single metal ion.
What are the advantages of using flame photometry?
1) Very sensitive- they can detect even the tiniest amounts of substances.
2) Very fast and test can be automated.
3) Very accurate- they don’t involve human error, like manual analysis does.
What is a homologous series?
A homologous series is a group of chemicals that have similar chemical structures.
What are alkanes?
Alkanes are a homologous series.
What atoms do alkanes contain?
Alkanes contain just carbon and hydrogen atoms
What is the general formula of alkanes?
CnH2n+2
What do different alkanes have?
Different alkanes have different lengths
What is the formula for methane?
CH4
What is the formula for ethane?
C2H6
What is the formula for propane?
C3H8
What is the formula for butane?
C4H10
Are alkanes saturated or unsaturated?
Alkanes are saturated as all the atoms have formed bonds with as many other atoms as they can.
Alkanes DO NOT have double carbon bonds.
What do members of a homologous series contain?
The same functional group
Are alkenes part of the homologous series?
Yes
What are alkenes?
Alkenes are part of the homologous series with one carbon double bond.
What is the general formula for alkenes?
CNH2N
This means that they have twice as many hydrogen as carbons.
Why are alkenes known as unsaturated?
As they can make more bonds- the double bond can open up, allowing two carbon atoms to bond with other atoms.
What is the formula for ethene?
C2H4
What is the formula for propene?
C3H6
What is the formula for But-1-ene?
C4H8
What is the formula for But-2-ene?
C4H8
What is the difference between But-1-ene and But-2-ene?
In but-1-ene the double bond is at the beginning or the end of the chain, but in but-2-ene the double bond is in the middle.
How can you test for alkene using bromine water?
When shaken together, an alkene will decolourise bromine water, turning it from orange to colourless. This is because an addition reaction takes place where bromine is added across the alkene double bond.
Why doesn’t alkane react with bromine water?
As they don’t contain double bond