Topic 9 - Separate Chemistry 2 Flashcards
In the flame test, what flame does lithium give?
Red
In the flame test, what flame does calcium give?
Orange-red
In the flame test, what flame does sodium give?
Yellow
In the flame test, what flame does potassium give?
Lilac
In the flame test, what flame does copper give?
Blue-green
In the flame test, what metal gives the red flame?
Lithium
In the flame test, what metal gives the orange-red flame?
Calcium
In the flame test, what metal gives the yellow flame?
Sodium
In the flame test, what metal gives the blue flame?
Copper
In the flame test, what metal gives the purple colour?
Potassium
How do you carry out a flame test?
Clean a wire loop with hydrochloric acid and then rinse it with distilled water
Then dip the loop into a sample of a metal compound and put it into a bunsen and record the colour
What do metal ions form with sodium hydroxide?
A coloured precipitate
What are metal ions mixed with to form a coloured precipitate?
Sodium hydroxide (NaOH)
How do you test metals for coloured precipitates?
Add a few drops of sodium hydroxide
What colour preciptate is formed when aluminium is added?
White
When NaOH is in excess, what precipitate is formed when added to aluminium?
Colourless
Why does NaOH is in excess and aluminium form the colourless solution?
Because the aluminum hydroxide is redissolved
What colour is formed when calcium is added to sodium hydroxide?
White
What metal forms white when it’s added to sodium hydroxide?
Aluminium or Calcium
What colour is formed when copper is added to sodium hydroxide?
Blue
What metal forms blue when added to sodium hydroxide?
Copper
What colour is formed when iron(ii) is added to sodium hydroxide?
Green
What metal forms green when added to sodium hydroxide?
Iron(ii)
What colour is formed when iron(iii) is added to sodium hydroxide?
Brown
What metal forms brown when added to sodium hydroxide?
Iron(iii)
What does adding sodium hydroxide to ammonium ions produce?
Ammonia
How do you tell if a substance contains ammonium ions?
By adding sodium hydroxide
How do you test for ammonia gas?
By holding a piece of damp red litmus paper over it and if ammonia is present the litmus paper will turn blue
How do you test for ammonia gas?
By holding a piece of damp red litmus paper over it and if ammonia is present the litmus paper will turn blue
A compound is heated in a flame
A lilac flame is produced
What does this show?
The compound contains potassium
A few drops of sodium hydroxide are added to an unknown solution
A brown precipitate forms
What does this tell you about the solution?
The solution is iron(iii)
How do you test for halide ions?
By adding silver nitrate
What precipitate does chloride give?
White
What halide ion gives a white precipitate?
Chloride
What precipitate does bromide give?
Cream
What halide ion gives a cream precipitate?
Bromide
What precipitate does iodide give?
Yellow
What halide ion gives a yellow precipitate?
Iodide
How do you test for carbonates?
By adding dilute acid
What is the positive result of the carbonate result?
Fizzing (carbon dioxide gas)
What is the equation for a positive result of the carbonate test?
Carbonate Ions + Acid -> Carbon Dioxide + Water
CO3^2- + 2H+ -> CO2 + H2O
What is the test for carbon dioxide gas?
Bubbling the gas through limewater, if carbon dioxide is present, the limewater will turn milky
How do you test for sulfate ions?
By adding dilute HCL and then adding barium chloride, and if sulfate ions are present a white precipitate of barium sulfate will form
What is the equation for a positive result of the sulfate ion test?
Barium Ions + Sulfate Ions -> Barium Sulfate
Ba^2+ + SO4^2- -> BaSO4
When testing for sulfate ions, why is dilute HCL added?
To stop any precipitation reactions not involving sulfate ions from taking place
A chemist adds some dilute nitric acid to X, followed by some silver nitrate solution
A yellow precipitate forms
What does this tell the chemist about X?
It contains iodide
What type of method is flame photometry?
An instrumental method
What does flame photometry allow you do to?
Identify ions in a dilute solution
What does the intensity of a measured wavelength mean in flame photometry?
The higher the concentration of that ion in solution
How do you use the calibration curve to work out the concentration of ions in a sample?
Find the intensity on the y-axis
Travel along horizontally from this point until you reach the curve
Draw a straight line down to the x-axis and read off concentration
Why is flame photometry more useful than flame tests?
Because it can be used to identify different ions in mixtures
What are the advantages of using instrumental analysis (machines) to analyse unknown substances?
They’re very sensitive
They’re very fast
They can be automatic
They’re very accurate (don’t involve human error)
Give two advantages of using flame photometry rather than using flame tests to identify ions?
Any two from: Machines are very sensitive Machines are very fast Machines are very accurate Flame photometry can be used to identify the metal ions in mixtures
What are alkanes
Saturated hydrocarbons
What is the alkane general formula?
C nH 2n +2
What does saturated mean?
All the atoms have formed bonds with as many other atoms as they can
What is a function group?
A group of atoms that determine how a molecule reacts
What is the function group of alkenes?
The C=C double bond
What is alkene general formula?
C nH 2n
What is the ratio of carbon to hydrogen in alkenes?
1 carbon to 2 hydrogen
What does unsaturated mean?
Not all the atoms have formed bonds with as many other atoms as they can
What do you add to test for alkene?
Bromine water
How do you do test for alkenes?
By shaking it with bromine and it decolourising
Why does the alkene test work?
Because the alkene loses the double bond and the bromine is added to it
Whats the colour change for the bromine water test?
Orange to colourless if alkene is present
What happens to hydrocarbons in combustion reactions?
They’re oxidised