Describe the preparation of potassium di | Class 12 Chemistry Chapter The d-and f-Block Elements, The d-and f-Block Elements NCERT Solutions

Question:

Describe the preparation of potassium dichromate from iron chromite ore. What is the effect of increasing pH on a solution of potassium dichromate?

Answer:

Potassium dichromate is prepared from chromite ore (FeCr2O4) in the following steps.

Step (1):

Preparation of sodium chromate

4FeCr2O4     +   16NaOH   +   7O2    →      8NaCrO4    +   2Fe2O3  +  8H2O

 

Step (2):

Conversion of sodium chromate into sodium dichromate

2Na2CrO4 + conc.H2SO4    →   Na2Cr2O7  +  Na2SO4  +  H2O

 

Step(3): Conversion of sodium dichromate to potassium dichromate

Na2Cr2O7    +   2KCl       →       K2Cr2O7   +   2NaCl

 

Potassium dichromate being less soluble than sodium chloride is obtained in the form of orange coloured crystals and can be removed by filtration.

The dichromate (Cr2O2-7) ion exists in equilibrium with chromate (CrO2-4) ion at pH 4. However, by changing the pH, they can be interconverted.


Study Tips for Answering NCERT Questions:

NCERT questions are designed to test your understanding of the concepts and theories discussed in the chapter. Here are some tips to help you answer NCERT questions effectively:

  • Read the question carefully and focus on the core concept being asked.
  • Reference examples and data from the chapter when answering questions about The d-and f-Block Elements.
  • Review previous year question papers to get an idea of how such questions may be framed in exams.
  • Practice answering questions within the time limit to improve your speed and accuracy.
  • Discuss your answers with your teachers or peers to get feedback and improve your understanding.

Comments

  • Sapna
  • 2019-03-07 10:03:54

What is the use of studying this


  • shahzad
  • 2019-01-29 15:45:12

there is a mistake in Na balancy


  • sahil jariyal
  • 2018-12-17 17:48:12

very good


  • Rahul sidhu
  • 2018-12-16 12:13:19

Thanks


  • Kunal
  • 2018-03-11 16:45:03

The product of 1st reaction is 8Na2CrO4 instead of 8NaCrO3


  • R K Navik
  • 2018-01-15 22:23:35

Very nice illustration


  • Imran
  • 2017-09-22 12:04:52

How chromite ore react with potassium carbonate


  • Sandeepa
  • 2017-09-17 19:28:17

This is very helpful for me


Comment(s) on this Question

Welcome to the NCERT Solutions for Class 12 Chemistry - Chapter . This page offers a step-by-step solution to the specific question from Excercise 2 , Question 14: Describe the preparation of potassium dichromate from iron chromite ore. What is the effect of incre....