Redox and Qualitative analysis of ions

Question 1

What are the rules regarding redox numbers

Answer 1

Redox numbers represent the valency or charge. Their proper name is “states”. They must always add up to 0, and H is always 1+, O is always 2-, Aluminium is 3+, Flourine is 1-, and chlorine is 1-

Question 2

Define oxidation

Answer 2

Oxidation is the loss of electrons, the loss of hydrogen, or the gain of oxygen

Question 3

What is the test for CO3 2-

Answer 3

Any acid is added and effervescence will be observed. To make sure this is CO2 it can be bubbled through limewater to make it cloudy.

Question 4

What is the test for SO4 2-

Answer 4

HCl is added to ensure no other chemicals affect the test, then BaCl is added. The solution will go from clear to cloudy and opaque, a white colour.

Question 5

Test for halides

Answer 5

Nitric acid is added to remove any chemicals that could result in confusing results, then AgNO3 is added. Cl- goes white, Br- goes cream, I- goes yellow. Cl- is soluble in dilute aqueous ammonia, Br- is soluble in concentrated, and I- is not soluble at all.

Question 6

Test for NH4+

Answer 6

Warm with NaOH and test for ammonia gas with a damp red litmus - it should turn blue

Question 7

Test for cations

Answer 7

Add NaOH solution. Cu 2+ will make a light blue solution with a precipitate, Fe 2+ will make a dark green solution with a precipitate, Fe3+ will make an orange/brown solution with a precipitate and Mn 2+ will make a pale pink solution with a white precipitate, Cr3+ will make a pale green solution with a precipitate, which will dissolve to form a deep green solution with excess NaOH

Question 8

What is the order for anion tests?

Answer 8

Cobra Snakes Hate Aardvarks

Carbonate Sulfate Halide Ammonium