Part D - The Chromate/Dichromate Equilibrium System With Barium Method 1. Place

Question

Part D - The Chromate/Dichromate Equilibrium System With Barium Method 1. Place 0.1 M K2Cr04 (20 drops) in a clean test-tube. Add 2 M NaOH (5 drops). Add, a drop at a time, 0.1 M Ba(NO3)2 until you notice a change. If you get to 10 drops added without any observable change, consult your demonstrator. Record your observations on the results page To this test-tube add drop by drop 2 M HNOg until a change is noted. Record your observations. Place 0.1 M K2Cr207 (20 drops) in a clean test-tube. Add 2 M HNO3 (5 drops). Add, a drop at a time, 0.1 M Ba(NO3)2 to a maximum of 10 drops. Record in pen your observations on the results page. To this test-tube add, drop by drop, 2 M NaOH until a change is noted. Record your observations. Rinse all test tubes with 2 mL of 2 M HNOs followed by plenty of water. Complete all equations. 2, 3. .4./ 5. 6.

Explanation / Answer

Tube for reaction 1 and 2:

Initial:

K2CrO4 + Ba(NO3)2 + 2NaOH = Ba(OH)2 + Na2CrO4 + 2KNO3

After adding HNO3 :

2 HNO3 + Ba(OH)2 = Ba(NO3)2 + 2 H2O

Tube for reaction 3 and 4:

Initial :

K2Cr2O7 + Ba(NO3)2 + HNO3 = BaCr2O7 + KNO3 + H+ + NO3-

After adding NaOH:

H+ + NO3- + NaOH = H2O + NaNO3

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