3.5 - Chemical Analysis Flashcards
What is the test for oxygen?
Oxygen re-lights a glowing splint
What is the carbon dioxide test?
Carbon dioxide turns clear limewater milky
How to test for ammonia gas?
It will change damp red litmus paper blue
What are the colours sodium, calcium, copper and potassium in the flame tests?
Sodium- yellow/orange
Potassium- lilac
Calcium- brick red
Copper- green
Describe how you would do a flame test
- Dip a clean wire loop in the acid to clean it
- Dip a clean wire loop in the sample solution
- Hold the flame test wire loop at the edge of a Bunsen flame
- Observe the changed colour in the flame
Why do we add sodium hydroxide to transition metals?
Because their hydroxides are insoluble in water
- if a solution of any soluble metal compound is mixed with sodium hydroxide then we get a displacement reaction. The sodium displaces a transition metal from its compound
- a transition metal hydroxide is formed as a result
- as it is insoluble it is a precipitate
What colour, word and symbol equation is observed when Iron 2 reacts with sodium hydroxide?
-green
Iron sulfate + sodium hydroxide = iron hydroxide + sodium sulfate
FeSO4 + 2NaOH = Fe(OH)2 + Na2SO4
Fe2+ + 2OH- = Fe(OH)2
What colour, word and symbol equation is observed when Iron 3 reacts with sodium hydroxide?
-red brown
Iron nitrate + sodium hydroxide = iron hydroxide + sodum nitrate
Fe(NO3)3 + 3NaOH = Fe(OH)3 + 3NaNO3
Fe2+ + 3OH- = Fe(OH)3
What word, symbol equation and colour can be observed when reacting copper with sodium hydroxide?
-blue
Copper sulfate + sodium hydroxide = copper hydroxide + sodium sulfate
CuSO4 + 2NaOH = Cu(OH)2 + Na2SO4
Cu2+ + 2OH- = Cu(OH)2
How do we test for halide (negative) ions?
Add dilute nitric acid to remove impurities and then silver nitrate
What non metal corresponds with which colour precipitate?
Chloride - white
Bromide - cream
Iodide - yellow
An example word, symbol and ionic equation for a halide ion
Sodium chloride + silver nitrate = silver chloride + sodium nitrate
AgNO3 + NaCl = AgCl + NaNO3
Ag+ + Cl- = AgCl
How to test for a carbonate ion?
When an acid reacts with a carbonate then fizzing is observed
-bubbles are CO2
How to test for a sulfate ion?
Add dilute hydrochloric acid followed by barium chloride
-when there is a sulfate ion then a white precipitate is seen
How to test for an alcohol?
- add oxygen so they are carboxylic acids with acidified potassium dichromate
- solution turns green
