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To an acidified dichromate solution, a pinch of Na2O2 is added and shaken. What is observed.
- a)Blue colour
- b)Orange colour changing to green
- c)Copious evolution of oxygen
- d)Bluish-green precipitate
Correct answer is option 'A,C'. Can you explain this answer?
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To an acidified dichromate solution, a pinch of Na2O2is added and shak...
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Observation:
- Blue color
- Copious evolution of oxygen
Explanation:
When a pinch of Na2O2 is added to an acidified dichromate solution and shaken, two reactions occur:
Reaction 1:
Na2O2 + H2SO4 → Na2SO4 + H2O2
In this reaction, Na2O2 reacts with H2SO4 to form Na2SO4 and H2O2 (Hydrogen Peroxide).
Reaction 2:
H2O2 + 2Cr2O7^-2 + 2H+ → 4Cr3+ + 5O2 + 2H2O
In this reaction, H2O2 reacts with dichromate ions (Cr2O7^-2) and protons (H+) in the presence of acid to form chromium ions (Cr3+), oxygen gas (O2), and water (H2O).
Explanation of Observations:
- Blue color: The blue color observed is due to the presence of chromate ions (CrO4^-2) in the dichromate solution. When Na2O2 is added, it reacts with the acid to form hydrogen peroxide, which further reacts with dichromate ions. This reaction results in the reduction of dichromate ions to chromium ions, leading to a decrease in the concentration of chromate ions and a decrease in the blue color intensity.
- Copious evolution of oxygen: The reaction between hydrogen peroxide and dichromate ions results in the formation of oxygen gas. This evolution of oxygen is observed as bubbling or effervescence in the solution.
Therefore, the correct observations for adding Na2O2 to an acidified dichromate solution are a blue color and copious evolution of oxygen.
- Blue color
- Copious evolution of oxygen
Explanation:
When a pinch of Na2O2 is added to an acidified dichromate solution and shaken, two reactions occur:
Reaction 1:
Na2O2 + H2SO4 → Na2SO4 + H2O2
In this reaction, Na2O2 reacts with H2SO4 to form Na2SO4 and H2O2 (Hydrogen Peroxide).
Reaction 2:
H2O2 + 2Cr2O7^-2 + 2H+ → 4Cr3+ + 5O2 + 2H2O
In this reaction, H2O2 reacts with dichromate ions (Cr2O7^-2) and protons (H+) in the presence of acid to form chromium ions (Cr3+), oxygen gas (O2), and water (H2O).
Explanation of Observations:
- Blue color: The blue color observed is due to the presence of chromate ions (CrO4^-2) in the dichromate solution. When Na2O2 is added, it reacts with the acid to form hydrogen peroxide, which further reacts with dichromate ions. This reaction results in the reduction of dichromate ions to chromium ions, leading to a decrease in the concentration of chromate ions and a decrease in the blue color intensity.
- Copious evolution of oxygen: The reaction between hydrogen peroxide and dichromate ions results in the formation of oxygen gas. This evolution of oxygen is observed as bubbling or effervescence in the solution.
Therefore, the correct observations for adding Na2O2 to an acidified dichromate solution are a blue color and copious evolution of oxygen.
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To an acidified dichromate solution, a pinch of Na2O2is added and shaken. What is observed.a)Blue colourb)Orange colourchanging to greenc)Copious evolution of oxygend)Bluish-green precipitateCorrect answer is option 'A,C'. Can you explain this answer?
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