What Does a Muddy Precipitate Indicate in a Redox Reaction?

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SUMMARY

The discussion centers on the implications of a muddy precipitate formed during a redox reaction involving an orange solution of substance 'A' and an unpleasant smelling gas. The solid precipitate indicates a reduction process, likely involving either dichromate ions (Cr2O7)2- or ferric ions (Fe3+), both of which yield a green solution upon reduction. The gas involved is identified as a reducing agent, with potential candidates including ammonia (NH3), sulfur dioxide (SO2), nitrogen dioxide (NO2), hydrogen sulfide (H2S), and chlorine (Cl2). Further experimentation is suggested to confirm the identity of the gas and the nature of the precipitate.

PREREQUISITES
  • Understanding of redox reactions and oxidation states
  • Familiarity with chemical equilibria and solubility rules
  • Knowledge of common gases and their chemical properties
  • Experience with qualitative analysis in chemistry
NEXT STEPS
  • Investigate the reduction mechanisms of dichromate ions (Cr2O7)2- and ferric ions (Fe3+)
  • Learn about the properties and reactions of sulfur dioxide (SO2) as a reducing agent
  • Explore the qualitative analysis techniques for identifying gases in chemical reactions
  • Study the effects of concentrated hydrochloric acid (HCl) on various precipitates
USEFUL FOR

Chemistry students, educators, and researchers interested in redox reactions, qualitative analysis, and the behavior of gases in solution.

AikiGirl
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Homework Statement


"State what you would infer from each of the following observations and suggest experiments you would carry out to test the validity of your inferences: When an unpleasant smelling gas was bubbled into an orange solution of a substance 'A', a solid was formed and the mixture appeared muddy in colour. On warming with conc HCl, some of the solid dissolved and the solution appeared green in colour."


Homework Equations


This is what I came up with:
Possible gases: NH3, SO2, NO2, H2S, Cl2
Possible solns: Br2, (Cr2O7)2-, Fe3+


The Attempt at a Solution



The soln is either (Cr2O7)2- or Fe3+ because they both are reduced to a green soln.

So the gas should be oxidised.

NH3: (NH4)- (same oxidation state)
SO2: (SO3)2- (same oxidation state), (SO4)2- (no ppt),
NO2: (NO3)- (same oxidation state),
H2S: S (yellow ppt), SO2 (gas), (SO3)2-, (SO4)2- (no ppt),
Cl2: Cl- (mostly soluble)

That's what I can figure out, not sure if it's correct, and not sure where to go from here. Any help would be appreciated.
 
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AikiGirl said:
The soln is either (Cr2O7)2- or Fe3+ because they both are reduced to a green soln.

So the gas is a reducing one.

Note: gas can reduce the substance in solution, but the precipitate doesn't have to contain reduced form of the gas - it can as well contain gas in the form introduced (protonated/neutralized depending on circumstances).
 

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