Courses
Courses for Kids
Free study material
Offline Centres
More
Store Icon
Store
seo-qna
SearchIcon
banner

How is sodium chromate converted into sodium dichromate in the manufacture of potassium dichromate from chromite ore ?
a.) By the action of concentrated sulphuric acid
b.) By roasting with soda ash
c.) By the action of sodium hydroxide
d.) By the action of limestone

Answer
VerifiedVerified
509.7k+ views
1 likes
like imagedislike image
Hint: The chromite ore contains the chromite ions in combination with iron. The sodium hydroxide replaces sodium with iron. Initially, chromite ions are present only which are converted to dichromate by sodium.

Complete step by step answer:
Initially, we will see the process of manufacture of potassium dichromate from chromite ore. Let us see that, then we will be able to get our answer.

This is a three step process.
Step 1 :- The first step involves the preparation of sodium chromate. The reaction can be written as -
4FeCr2O4+16NaOH+7O28NaCrO4+2Fe2O3+8H2O

Step 2 :- The step 2 involves the conversion of sodium chromate into sodium dichromate. The reaction is
2Na2CrO4+conc.H2SO4Na2Cr2O7+Na2SO4+H2O

The sodium chromate produced in the first step reacts with concentrated sulphuric acid to give the sodium dichromate along with sodium sulphate and water.

Step 3 :- The step 3 involves the conversion of sodium dichromate and potassium dichromate.
Na2Cr2O7+2KClK2Cr2O7+2NaCl

After this, we get orange precipitates of potassium dichromate.
So, by observing the above, mechanism; we can conclude that the conversion of sodium chromate in sodium dichromate is by action of concentrated sulphuric acid.
So, the correct answer is “Option A”.

Note: The potassium dichromate is less soluble than sodium chloride. Thus, it can be removed by filtration. It must also be noted that the dichromate ions are in equilibrium with the chromate ions at pH 4. On changing the pH value, the ions can be interconverted into each other as per the requirement of the reaction.
Latest Vedantu courses for you
Grade 8 | CBSE | SCHOOL | English
Vedantu 8 CBSE Pro Course - (2025-26)
calendar iconAcademic year 2025-26
language iconENGLISH
book iconUnlimited access till final school exam
tick
School Full course for CBSE students
EnglishEnglish
MathsMaths
ScienceScience
₹49,800 (9% Off)
₹45,300 per year
Select and buy