A simple experiment to determine an unknown powder

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Discussion Overview

The discussion revolves around a homework problem involving the identification of an unknown white powder that could be one of six substances. Participants explore various experimental methods to determine the identity of the powder using chemical reactions and indicators, focusing on the theoretical and practical aspects of the proposed tests.

Discussion Character

  • Homework-related, Experimental/applied, Technical explanation

Main Points Raised

  • One participant suggests reacting the powder with acetic acid to check for bubbling, indicating the presence of a carbonate.
  • Another participant inquires about the solubility of silver carbonate and silver sulfate, potentially to inform their testing strategy.
  • A different participant proposes using phenolphthalein to determine if the powder is basic, which would help classify the substances broadly.
  • One participant reiterates the acetic acid test and adds that continuing to add powder after bubbling ceases can help assess the solubility of the powder, suggesting the use of spent acid as a water source for testing.

Areas of Agreement / Disagreement

Participants present various methods and considerations for identifying the unknown powder, but there is no consensus on the best approach or the effectiveness of the proposed tests. Multiple competing views on experimental methods remain.

Contextual Notes

Some participants express uncertainty about the solubility of certain compounds and the availability of materials for testing, which may limit the experiments' effectiveness.

Who May Find This Useful

Students or individuals interested in chemistry experiments, particularly those focused on qualitative analysis and identification of substances through chemical reactions.

Zaros
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Homework Statement


You are given a white powder and it could be one of six substances: calcium carbonate, calcium sulfate, sodium hydrogen carbonate, sodium carbonate, sodium chloride and sodium hydroxide. Determine the unknown sample.
Materials: White powder (5g)
Phenolphthalein
Silver nitrate solution
Acetic acid

The Attempt at a Solution


React with acetic acid if it is a carbonate it will bubble (CO2 formed)

React with the silver nitrate solution if it is sodium chloride it will form a cloudy white solution:
AgNO3 + NaCl → AgCl(s) + NaNo3

Now the phenolphthalein changes from colourless to pink when the pH goes above 8.2 so I assume there is some way to find out which one using basic acidic but this is where I start to have trouble as I am unsure what other experiments to do.
Thanks for the help
 
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What is the solubility of silver carbonate? Silver sulfate?
 
I'd like to first use phenolphthalein to check whether the given salt is basic or not. It will really classify them in broad sense.

Check how many are basic enough to give positive tests with phenolphthalein?
 
Zaros said:
React with acetic acid if it is a carbonate it will bubble (CO2 formed)
If you continue to add powder to a sample of acetic acid after bubbling ceases, you will be able to see whether that powder is soluble (i.e., forms an aqueous solution).

You aren't provided with water to test the powders for solubility, so use some spent acid as your water source.
 

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