November 28, 2015

Homework Help: Chemistry

Posted by Fiona on Friday, April 13, 2007 at 12:34am.

Given four unlabeled compounds and four labels (potassium sulfate, potassium carbonate, chromium sulfate, and cobalt bromide) is there a simple test that will allow correct labelling of each compound?

I take we are looking for a simple school lab type test?
If only allowed one reagent then consider the following properties:

cobalt (II) bromide is green (the hydrate is is a reddy violet colour)

chromium (III) sulfate (usually a hydrate) is violet

potassium sulfate is white, colourless solution in water.

potassium carbonate is white, colourless solution in water and evolves CO2 with acid.

Post your answer if you want to check it.

Dr Russ
The question states two of the compounds are white solids and the other two are green solutions.
I had already found out that the two potassium compounds are white solids and cobalt bromide is green. I couln't find out the colour of chromium sulfate (but had assumed it was green because of the question), so thank you for that. What would turn a solution of chromium sulfate green?

I had worked out all of your clues, but I just don't know the answer.
I am studying Yr 12 Chemistry, but have not done Yr 11. Is there something I should have learnt but haven't yet?

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