Topic 8.4-8.6 Flashcards
What are the tests for (positive or negative)
Flame test and Precipitation reactions
positive
What are the tests for anions (positive or negative)
carbonation ions, halide ions, sulfate ions
Negative
What is the method for the flame test
- Use a metal wire which you first put in HCl to get rid of any contamination
- dip the wire into your compound and put it in your flame
What colour does the flame turn with Li+ (Lithium)
Crimson
What colour does the flame turn with Na+ (Sodium)
Yellow
What colour does the flame turn with K+ (Potassium)
Lilac
What colour does the flame turn with Ca2+ (Calcium)
Red/Orange
What colour does the flame turn with Cu2+ (Copper)
Blue/Green
What is the method for a precipitate reaction
Add sodium hydroxie to an unkown solution. We make a insoluble solid called a precipitate
what is the result of the precipitate reaction for Aluminium and what happens with excess sodium hydroxide
Colour: White
result with excess: precipitate dissolves
what is the result of the precipitate reaction for Calcium and what happens with excess sodium hydroxide
Colour: White
result with excess: precipitate dissolves
what is the result of the precipitate reaction for Magnesium and what happens with excess sodium hydroxide
Colour: White
Result with excess: precipitate remains
what is the result of the precipitate reaction for copper
Blue precipitate
what is the result of the precipitate reaction for Iron (II)
green precipitate
what is the rEsult of the precipitate reaction for Iron (III)
brown precipitate
what is the genereal ionic equation for precipitate reactions
ion^n+ +nOH^- —-> ion(OH)n
What is the method to test carbonate ions
- add acid to the sample
- bubble the gas produced through lime water
-it will turn cloudy of carbon dioxide is present
What is the method to test halide ions (ions from group ___)
group 7
- add nitric acid and silver nitrate to the unknown solution
What is the colour of the precipitate when chloride is present
White
What is the colour of the precipitate when Bromide is present
Cream
What is the colour of the precipitate when iodide is present
yellow
What is the method for testing for sulfate ions and how do we recognise a positive result
- add nitric acid to unkown solution
- then add barium chloride
- We will see a white precipitate
Why do we add nitric acid to the test for halide ions and sulfate ions
because it removes any carbonate ions which could give a false positive
