1chemical tests Flashcards
ammonia test
damp red litmus paper turns blue
carbon dioxide test
bubble through lime water and then lime water goes cloudy
chlorine test
damp blue litmus paper and then paper is bleached
hydrogen test
hold a lighted splint to mouth of test tube and then burns with a squeaky pop sound
oxygen test
hold a glowing splint- splint then relights
a flame test is to
identify metal ions by the colour of flame they produce
how to take a flame test
Dip the loop of an unreactive metal wire such as nichrome or platinum in concentrated acid, and then hold it in the blue flame of a Bunsen burner until there is no colour change
This cleans the wire loop and avoids contamination
This is an important step as the test will only work if there is just one type of ion present
Two or more ions means the colours will mix, making identification erroneous
Dip the loop into the solid sample and place it in the edge of the blue Bunsen flame
Avoid letting the wire get so hot that it glows red otherwise this can be confused with a flame colour
colour of Li^+ flame
red
colour of Na^+ flame
yellow
colour of K^+ flame
lilac
colour of Ca^2+
orange-red
colour of Cu^2+
blue-green
metal cations in aqueous solution can be identified by
the colour of the precipitate they form on addition of sodium hydroxide and ammonia
results of cation hydroxide test on ammonia
ammonia gas produced turns damp red litmus blue
results of cation hydroxide test on copper (II)
light blue precipitate is formed
results of cation hydroxide test on iron (II)
green precipitate formed
results of cation hydroxide test on iron (III)
red-brown precipitate formed
test for anion carbonate
add dilute acid and test the gas released
test for anion chloride
acidify with dilute nitric acid and add silver nitrate
test for anion bromide
acidify with dilute nitric acid and add aqueous silver nitrate
test for anion iodine
acidify with dilute nitric acid and add aqueous silver nitrate
test for anion sulfate
acidify with dilute nitric acid and add aqueous barium nitrate
result for anion carbonate test
Effervescence, gas
prodduced is CO, which
turns limewater milky
result for anion chloride test
white precipitate formed
result for anion bromide test
cream precipitate formed
result for anion iodide test
yellow precipitate formed
result for sulfate iodide test
white precipitate formed
chemical test for water
Anhydrous copper(II) sulfate turns from white to blue on the addition of water
The equation is:
CuSO4 (s) + 5H2O (l) → CuSO4.5H2O (s)
physical test for water
A physical test to see if a sample of water is pure is to check its boiling point
A sample of the liquid is placed in a suitable container such as a boiling tube and gently heated
Using a thermometer, you can check if the boiling point is exactly 100 oC
Any impurities present will usually tend to raise the boiling point and depress the melting point of pure substance
