chem tests Flashcards
How is carbon dioxide tested?
Bubbling the gas through limewater, lime water is calcium hydroxide. carbon dioxide reacts to form white precipitate of calcium carbonate.
Limewater turns cloudy white if carbon dioxide is present.
What color does limewater turn in the presence of carbon dioxide?
Cloudy white
This is due to the formation of calcium carbonate.
What is the test for chlorine gas?
Damp blue litmus paper turns red and then bleaches white
Chlorine is toxic and should be handled in a fume cupboard.
what is the test for hydrogen gas?
a lighted splint is held to the mouth of the tube, the hydrogen explodes with a squeaky pop. It combines with air to make water
What sound indicates the presence of hydrogen gas during testing?
‘Squeaky pop’ sound
This occurs when hydrogen burns with oxygen to form water.
what’s the test for oxygen?
a glowing splint is put into tube containing gas, oxygen relights a glowing splint.
This confirms the presence of oxygen gas.
What happens to damp red litmus paper in the presence of ammonia?
Turns blue
This indicates the basic nature of ammonia.
what’s the test for anhydrous copper(II) sulfate
add water, will turn from white to blue.
This indicates the presence of copper(II) cations.
What boiling point indicates the purity of water?
Exactly 100 °C
Impurities tend to raise the boiling point of water.
What is the purpose of a flame test?
To identify positive metal ions by the color of the flame
Different metal ions produce different flame colors.
how to conduct flame test
a platinum/ nichrome wire is dipped into concentrated HCL acid and then into salt needed to test. held within a non luminous flame.
Cloudiness in limewater indicates the presence of carbonate ions.
What color flame is produced by lithium ions
Red
This is a specific identification for lithium cation.
sodium ions
yellow
potassium
purple
copper
blue-green
calcium
orange- red
test for cations
dissolve salt in pure water, add sodium hydroxide solution.
A white precipitate of barium sulfate indicates the presence of sulfate ions.
test for copper(II) ions
forms blue precipitate of copper(II) hydroxide.
This is a chemical test for the presence of water.
Test for Iron(III) ions
forms orange-brown precipitate of iron(III) hydroxide.
While chlorine has a distinctive smell, it is not an acceptable means of identification.
Test for Iron(II) ions
forms a green precipitate of iron(II) hydroxide.
Using nitric acid prevents interference from chloride ions present in hydrochloric acid.
test for ammonium ions
- sodium hydroxide to produce ammonia gas (you can smell the pungent smell)
- turns red litmus paper blue as its alkaline.
safety precosions of ammonium ions test
don’t smell gas if you have breathing problem such as asthma.
don’t smell mixture when warm as there’s much more gas present.
test for carbonates
add HCL acid and look for fizzing/ bubbling of gas. test the gas by bubbling it through limewater to test for carbon dioxide.
test for sulfates
add water to make solution and then add HCL acid. Add barium chloride solution . A sulfate will produce a white precipitate of barium sulfate.
test for chlorides, bromides and iodides.
make a solution and add nitric acid to make it acidic. Then add silver nitrate solution.
chlorine ions color
white precipitate of silver chloride.
iodide ions color
yellow precipitate of silver iodide.
bromide ions color
cream precipitate of silver bromide.
