reactions/tests Flashcards
How do you carry out a flame test?
- Dip a clean wire loop into the solid compound being tested
- Put the loop into the blue flame
- Observe and record colour produced
What colour does Lithium give out?
Crimson
What colour does Sodium give out?
yellow
What colour does Potassium give out?
lilac
What colour does Calcium give out?
orange-red
What colour does Copper give out?
green
What dilute solution is used in metal ion tests?
sodium hydroxide
Are metal hydroxides soluble?
No
What is the precipitate colour given from Aluminium (Al3) + Sodium hydroxide? And how else do we identify it if excess sodium hydroxide is added?
White
Dissolves to form a colourless solution
What is the precipitate colour given from Calcium (Ca2) + Sodium hydroxide?
White
The precipitate is unchanged
What is the precipitate colour given from Magnesium (Mg2) + Sodium hydroxide?
White
The solution is unchanged
What is the precipitate colour given from Copper (Cu2) + Sodium hydroxide? (this is a transition metal)
Blue
What is the precipitate colour given from Iron II (Fe2) + Sodium hydroxide? (this is a transition metal)
Green
What is the precipitate colour given from Iron III (Fe3) + Sodium hydroxide? (this is a transition metal)
Brown
What is the test for Ammonia, 2NH3?
add sodium hydroxide and warm, a pungent smelling gas (white gas) is formed which turn red litnus paper blue
What is the test for a sulfate?
1.add a few drops of dilute hydrochloric to the sample
2.add a few drops of dilute barium chloride or barium nitrate solution
3.a white precipitate forms if sulfate ions are present
What is the test for the Group 7 elements?
The silver nitrate test.
What is the silver nitrate test?
- Add acid to sample
- Add silver nitrate
In the silver nitrate test what colour does Chlorine give off?
White
In the silver nitrate test what colour does Bromine give off?
Cream
In the silver nitrate test what colour does Iodine give off?
Yellow
In the reactivity series, when an element is below carbon, how do we separate it?
Displacement
In the reactivity series, when an element is above carbon, how do we separate it?
Electrolysis
Explain why, in a test for halide ions, dilute hydrochloric acid cannot be used to acidify the sample.
Hydrochloric acid, HCl(aq), contains chloride ions. These would react with silver ions in the test, giving a false positive result.
How is calcium oxide/quicklime formed?
calcium carbonate → calcium oxide + carbon dioxide
CaCO3(s) → CaO(s) + CO2(g)
What happens when water is added to calcium oxide?
calcium oxide + water → calcium hydroxide
CaO(s) + H2O(l) → Ca(OH)2(s)
The solid remains white but crumbles into a powder as the water is added.
What is calcium hydroxide also known as? What is used for?
Slaked lime
To neutralise excess acidity
Finish this reaction
calcium hydroxide + carbon dioxide →
calcium carbonate + water
What is the symbol equation for this reaction?
Ca(OH)2(aq) + CO2(g) → CaCO3(s) + H2O(l)
How do you test for alcohol?
Add acidified potassium dichromate
Positive test: orange-green
How do you test for alkene?
Bromine water
Positive test: orange-colourless
