Name: Lab Section Date Experiment IV: LeChatelier\'s Principle Lab Report I. Chr

Question

Name: Lab Section Date Experiment IV: LeChatelier's Principle Lab Report I. Chromate/dichromate ion equilibrium Reaction: Yellow 1. What is color of the initial solutign in the test tube? Cro; (aq) +2H' (aq)CrO: (aq) + H,O(1) Orange Color After the addition of 6 M N addition of NaOH affect the chromate/dichromate equilibrium? How does this relate to the change, if any, in the color of the solution? Include equations for reactions 2. test tube, what is the color of the solution? How does the xplanation. Color: After the addition of 3 M H,S, addition of H2SO, affect the chromate/dichromate equilibrium? How does this relate to the change, if any, in the color of the solution? Include equations for reactions to the test tube, what is the color of the solution? How does the r explanation. test 3. Color:

Explanation / Answer

2.In addition of 6M NaOH in test tube containing Cr2O72-,it reacts with NaOH to give yellow colour Sodium Chromate(NaCrO4).The reaction is given below-

Cr2O72- + 2NaOH = 2CrO42- + H2O

CrO42- is Yellow in colour.That's why the orange solution turns into yellow.

3.After adding 3 M H2SO4 ,the yellow solution again turns into orange as the Chromate(CrO42-) formed in basic solution is converted into Dichromate(Cr2O72-).The equation is given below-

2CrO42-(aq) (yellow) + 2H+(aq) Cr2O72-(aq) (orange) + H2O(l)

Now the addition of H2SO4 favours the formation of Dichromate as it is more stable in acidic condition whereas in basic condition the formation of Chromate favours.

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