Question

Change of orange colour of chromium $\left( {{\text{VI}}} \right)$ to green colour of chromium $\left( {{\text{III}}} \right)$ indicates presence of a:
A.Reducing agent
B.Oxidizing agent
C.Reagent
D.Drying agent

Answer 1

The oxidation state of chromium changes from 6 to 3 that is the oxidation state decreased. The decrease in oxidation state is termed as reduction.

Complete step by step answer:
Due to the decrease in oxidation state of chromium, given in question, the oxidation number of chromium decreases and hence chromium is being reduced. The substances that are used to reduce others are known as reducing agents. There must be a reducing agent present in the solution in order to convert orange colour to green colour.

Hence the correct option is A.

Additional information:
Chromium is a d block element. The atomic number of chromium is 24. If it belongs to group number 6 and period number 4. The compound of chromium having the oxidation state 6 is dichromate ion. Under acidic conditions the dichromate ion converts themselves to the chromium ion with a charge of plus 3. The dichromate ion acts as a strong oxidizing agent in the acidic medium because it itself gets reduced. The substance that gets reduced itself will oxidize others and hence will act as an oxidizing agent. The dichromate ion in the form of potassium dichromate is used in laboratories for various purposes.

Note:
In a chemical reaction reactants are of two types one is called substrate and other one is called reagent. The reagents are further of many types such as oxidizing agents. Reducing agents, organo-metallic reagents etc. drying agents are the substance which dry out the system by absorbing water from the system.