Qualitative analysis

Question 1

what is quantitative analysis

Answer 1

measures the amount of each substance present in a sample

Question 2

what is qualitative analysis

Answer 2

investigates the types of substance present in a sample

Question 3

what are flame tests used for

Answer 3

to detect certain metal cations

Question 4

what are the flame colours for:

a) sodium
b) potassium
c) calcium
d) copper

Answer 4

a) yellow
b) lilac
3) red
d) blue/green

Question 5

describe tests for Al3+, Ca2+, Cu2+, Fe2+, Fe3+

Answer 5

dissolve the sample in water, then add a few drops of sodium hydroxide solution. metal cations in solution form insoluble precipitates when this is done. aluminium(white), calcium(white), copper(blue), iron(green), iron(brown)

Question 6

describe a test to show the presence of ammonium ions, NH4+, in a sample solution

Answer 6

mix the sample substance with sodium hydroxide solution. warm it using a Bunsen burner flame. if ammonium ions are present, ammonia gas is given off. ammonia has a distinctive smell, and it turns damp red litmus paper blue

Question 7

describe a test for Cl-, Br-, I- using dilute nitric acid and silver nitrate solution

Answer 7

add a few drops of nitric acid to the sample, then a few drops of silver nitrate solution. a different coloured precipitate forms, depending on the halide ion present: chloride(white), bromide(cream), iodide (yellow)

Question 8

give two ways in which chemists these tests

Answer 8

to test water purity and substances in blood

Question 9

describe testing water purity

Answer 9

Drinking water is not pure water becuase it contains dissolved substances. some of these are deliberately added to tap water:
> chlorine is added to kill harmful micro-organisms
> aluminium sulfate is added to remove small solid particles
it is important to make sure that the amount of each dissolved substance found in drinking water is safe

Question 10

describer testing blood

Answer 10

modern blood tests are very sensitive. they can detect and accurately measure very small amounts of substances in the blood.
analytical chemists test blood samples to help doctors identify why their patients are ill. for example, high levels of aluminium in the blood are linked with alzheimers disease

Question 11

how can we test for carbonate ions

Answer 11

By using dilute acid. add dilute hydrochloric acid to a sample containing carbonate ions, you will briefly see bubbles. the gas is carbon dioxide. it turns lime water milky.