Chemistry Test 68

Result

Chemistry Test 68

Score
-
out of -
Rank
-
out of -

TIME Taken - -

SHARING IS CARING

If our Website helped you a little, then kindly spread our voice using Social Networks. Spread our word to your readers, friends, teachers, students & all those close ones who deserve to know what you know now.

Weekly Quiz Competition

Question 1
4 / -1

Leaching involves the formation of a soluble complex of metal by addition of a chemical. Leaching of the silver ore is done by adding a solution of NaCN in the atmosphere of which of the following gases?

A
Nitrogen

B
Carbon dioxide

C
Oxygen

D
Neon

Solution

The reaction mixture of silver ore with the dilute solution of NaCN is aerated and the soluble complex of sodium dicyanoargentate(I) is formed, from which the silver metal is extracted by reduction of the complex with zinc.

4Ag⁺ + 8NaCN + 2H₂O + O₂ ⇌ 4Na[Ag(CN)₂] + 4NaOH

Zn + 2Na[Ag(CN)₂] → Na2[Zn(CN)₄] + 2Ag
Question 2
4 / -1

A considerable part of the harmful UV radiation of the sun does not reach the surface of Earth because of the formation of ozone in the stratosphere. However, a continuous decrease in the ozone levels has raised serious environmental issues because of the leaking in of the ultraviolet radiation into the Earth's atmosphere. Which of the following statements in this context is not true?

A
Ozone is formed in the stratosphere when oxygen molecules photodissociate after taking in ultraviolet photons.

B
Chlorofluorocarbons are highly reactive molecules and break down in the troposphere to release free radicals that destroy the ozone molecules

C
Ozone is a highly reactive molecule that easily reduces to the more stable oxygen form with the assistance of a catalyst.

D
Reactions that take place on polar stratospheric clouds (PSCs) play an important role in enhancing ozone depletion.

Solution

Statement 2 is incorrect because the chlorofluorocarbons are highly stable molecules and reach the stratosphere without breaking down in the troposphere.

In the stratosphere, the halogen free radicals are produced, which destroy the ozone molecules through a variety of catalytic cycles.
Question 3
4 / -1

Cyanide process is used for the extraction of

A
barium

B
aluminium

C
boron

D
gold