Discussion in 'Cambridge O Levels' started by Nibz, May 24, 2011.
hey!! Can any one give me a list of all the indicators and how they work? Thanks.
Oxygen is a poisonous gas , if we inhale it directly from an Oxygen source
We don't die from oxygen in air , because other gases are in the atmosphere with it
So I think nitrogen might be a poisonous gas if inhaled directly from the source
Its just an opinion
That was supposed to be 'Nitrogen Dioxide'!
For which substances can potassium dichromate be used as a test for?
Acid ( Red - Yellow) , Neutral ( Green) , Alkaline ( Blue - Violet)
Alkaline ( Pink) For Strong ( Colourless) , Neutral ( Colourless) , Acid ( Orange)
Alkaline: ( Yellow) , Neutral ( Colourless) , Acid ( Red)
P.S Some of the indicators have a trend in colour , such as methyl orange from 1-14 colour becomes more pale
Hope that helped,
Testing for Ethanol
To test for the presence of any reducing agent.
Doesn't phenolphthalein only change colour in alkalis? Isn't it supposed to be colourless in acids? and what about the bromo-something blue? what colour changes does that have? PLEASE HELP!
It gives colourless on weak acids
Acid (Yellow) , Neutral (Dark green) , Alkaline (Blue)
http://www.xtremepapers.me/CIE/Cambridg ... 9_qp_6.pdf can any help me with q5.. this questions come up a lot..and technique of doing these types. PLEASE HELP
Here are some Ion testing so you could solve the questions
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Hope it helps
Tatueg can you take me through one question like exactly how to do it
You have been given 3 Aqueous Solutions. K , L , M
L was identified as sodium hydroxide
The first question on the table says
"Ph of L" L is sodium hydroxide which is an alkali
Alkalis have a range of Ph from 8-14 . Sodium hydroxide is a strong alkali so you should provide any ph from the range of 11-14
2nd Question in the table says
What happens if we drop Sodium hydroxide on Copper sulphate
When Sodium hydroxide is added to Copper ion , a Blue precipitate is formed and does not dissolve in Excess of Sodium Hydroxide
Only when Excess ammonia is added , It dissolves giving a Pale blue solution as mentioned in the table
3rd Question in the table says
If Sodium Hydroxide was added to Aluminium Sulphate
Results would be
White precipitate , If in excess would dissolve giving a colourless solution
K is identified as Aqueous Ammonia
and M is identified as Hydrochloric acid duo to acidification and adding silver nitrate and forming a white ppt. which is a typical for a chloride ion test , Donot provide only chloride ion for 2 marks provide a chloride compound such as Hydrochloric acid.
Doesn't phenolphthalein only change colour in alkalis? Isn't it supposed to be colourless in acids? and what about the bromo-something blue? what colour changes does that have? PLEASE HELP![/quote]
It gives colourless on weak acids
Acid (Yellow) , Neutral (Dark green) , Alkaline (Blue)[/quote]
Thanks a lot. Just one more question - Does phenolphthalein change colours in strong acids and if it does, what colour change happens?
Again thank you so very much.
If only I had time!
You can do that, if possible !
how would i know when to use the right test for water for example :give a test for pure water in the ms they said boiling then the result is 100 but i wrote copper 2 sulphate and its result!! is that correct???thanks
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