When you entered your chemistry lab, you may have seen beakers with an orange liquid solution. It looks so beautiful, teachers ask you to do titrations using this orange solution.
You may have seen an orange strain on the apron which is used by researchers while performing experiments. Do you know what is the name of that compound?
Or what is the major element involved in this one?
Or how versatile is this compound?
We will study more about this coloured compound and see how useful is this in chemistry.
Table of content:
Potassium dichromate is found in nature as lopezite, an uncommon mineral. It is claimed to have been discovered as vug fills in the nitrate deposits of Chile's Atacama desert and South Africa's Bushveld igneous complex.
1. The action of heat on potassium dichromate:
The action of heat on potassium dichromate: Upon heating potassium dichromate, chromate is obtained along with oxygen gas. The reaction is as follows:
4K2Cr2O7(s) →4K2CrO4(s) + 2Cr2O3(s) + 3O2(g) ↑
2. The action of potassium dichromate on alkalis:
On reacting with alkalis, potassium dichromate loses its orange-red colour and turns yellow. The reaction is as follows:
3. Oxidizing properties of potassium dichromate:
When reacted with dilute sulphuric acid, one mole of potassium dichromate produces three moles of nascent oxygen gas is released. The reaction is as follows:
When potassium dichromate is reacted with KI, iodine gas is liberated. The reaction is as follows:K2Cr2O7(s)+4H2SO4(aq)4K2SO4(s)+Cr2(SO4)3(s)+7H2O(l)+3[O] (g)↑
The following are some of the most common industrial applications for potassium dichromate.
Q1. The coefficient of the proton in the reduction reaction of dichromate in an acidic medium is ____
In an acidic environment, the following is a representation of its reduction reaction of dichromate ion:
Q2. The reddish-brown gas evolved in the chromyl chloride test is ______
The chromyl chloride test is a qualitative analytical test for Cl- ion conformation.Potassium dichromate reacts with concentrated sulphuric acid to give reddish-brown vapours of chromyl chloride. This reaction is also called Chromyl Chloride Test. The reaction is as follows:
Q3. How do we use Potassium dichromate in drink and drive tests?
The colour of the orange dichromate-coated crystals changes from Cr(VI) orange to Cr(III)green when alcohol vapour comes into contact with them. The amount of alcohol in the suspect's breath is precisely proportional to the colour shift.
Q4. The oxidation number of chromium (Cr) in chromium peroxide is _______
Chromium peroxide can be prepared by treating it with H2O2 in an acidic medium. The reaction is
explained as follows:
The oxidation state of chromium in Chromium peroxide is +6
Q1. Is potassium dichromate safe to eat?
Answer: Consumption of even a small amount of potassium dichromate can be lethal. A dose of 40 g or more has been known to cause rapid mortality and severe adverse effects in humans.
Q2. Is potassium dichromate corrosive in nature?
Answer: The substance is highly corrosive in nature, and prolonged exposure can result in serious eye damage or blindness.
Q3. Why is K2Cr2O7 referred to as the primary standard solution?
Answer: Because it is exceedingly pure, stable, and does not fluctuate its concentration with environmental conditions, potassium dichromate solution is used as a primary standard solution
Q4. Why is K2Cr2O7 ineffective as a self-indicator?
Answer: Because potassium dichromate can only work as an oxidising agent in an acidic media, it cannot be employed as a self-indicator because its reduction product blocks the visual detection at the end of the reaction.
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