Potassium Dichromate

Part 2 of the series (d- and f- block). Question mode: Flashcards only. Answer mode: Answer with Definition. Suitable for JEE Mains, I don't know about JEE Advanced. Catered towards NCERT and IAT.

What (ore) is Potassium Dichromate from?

chromite or chrome iron

$FeO\cdot Cr_2O_3$ or $FeCr_2O_4$

What are the three basic steps of preparation of $K_2Cr_2O_7$?

1. Conversion of chromite into sodium chromate

2. Conversion of sodium chromate into sodium dichromate

3. Conversion of sodium dichromate into potassium dichromate

How is chromite converted to sodium chromate?

It is obtained by the fusion of chromite ore with sodium hydroxide or sodium carbonate in the presence of air ($O_2$).

What is the chemical reaction for conversion of chromite to sodium chromate using sodium carbonate?

What is the chemical reaction for conversion of chromite to sodium chromate using sodium hydroxide?

How is sodium chromate separated from ferric oxide?

by filtration

How is sodium chromate converted to sodium dichromate?

by acidification with sulphuric acid

What is the chemical reaction for conversion of sodium chromate to sodium dichromate?

How is sodium dichromate separated from sodium sulphate?

sodium sulphate is less soluble and crystalized out first on cooling the mixture

What is the colour of sodium dichromate?

orange

What is the colour of potassium dichromate?

orange

How is sodium dichromate converted to potassium dichromate?

It is treated with potassium chloride

What is the chemical reaction for conversion of sodium dichromate to potassium dichromate?

How is potassium dichromate separated from sodium chloride?

orange potassium dichromate crystals are crystallized out of the solution or whatever

What is the chemical reaction when you heat $K_2Cr_2O_7$?

What gas is evolved on the heating of potassium dichromate?

Oxygen

$Cr_2O_7^{-2}$ converts to $CrO_4^{-2}$ in ________ medium

(acidic, basic)

basic

$CrO_4^{-2}$ converts to $Cr_2O_7^{-2}$ in ________ medium

(acidic, basic)

acidic

Whta is the colour of $Cr_2O_7^{-2}$?

orange

What is the colour of $CrO_4^{-2}$?

yellow

What colour change do you observe when treating $K_2Cr_2O_7$ with an alkali?

orange turns to yellow

What is the chemical reaction for treating potassium dichromate with potassium hydroxide?

What happens when you acidify $K_2CrO_4$?

It changes back to $K_2Cr_2O_7$.

What is the melting point of potassium dichromate?

670 K

What is the chromyl chloride test?

potassium dichromate gives orange/red vapouds of chromyl chloride on heating with concentrated sulphuric acid and metal chlorides

What is the chemical reaction for the chromyl chloride test?

What is the chemical formula of chromyl chloride?

$$CrO_2Cl_2$$

What is the structure of the chromate ion?

What is the structure of the dichromate ion?

What is the bond angle between the $Cr-O-Cr$ bond?

126 degrees

What is the chemical equation for reaction of potassium dichromate with hydrogen peroxide?

What is the ionic chemical reaction that depits the oxidising nature of dichromates?

dichromate can oxidise $2I^-$ to?

$$I_2$$

dichromate can oxidise $2Cl^-$ to?

$$Cl_2$$

dichromate can oxidise $Fe^{+2}$ to?

$$Fe^{+3}$$

dichromate can oxidise $Sn^{+2}$ to?

$$Sn^{+4}$$

dichromate can oxidise $SO_2$ to?

$$SO_4^{-2}$$

dichromate can oxidise $H_2S$ to?

$$S$$

dichromate can oxidise $NO_2^-$ to?

$$NO_3^-$$

What is the oxidation state of $Cr_2O_7$ in potassium dichromate?

$$-2$$

What is the oxidation state of $Cr$ in potassium dichromate?

$$+6$$

What is the chemical equation for the reaction of potassium dichromate with potassium iodide?