Environmental Chemistry

Step 1: Identify thermosphere.
Thermosphere is the region of atmosphere above mesosphere, where UV and X-rays ionize gases.
So it contains ionized species and atomic oxygen.
Step 2: Check which option contains ions.
Only option (A) has:

These are typical thermospheric / ionospheric constituents.
Step 3: Conclude correct answer.
Thus, the chemical entities present in thermosphere are ionized oxygen and nitric oxide ions.
Final Answer:

Step 1: Type of radiation in radiography.
Radiographers are exposed mainly to X-rays and gamma rays.
Step 2: Best shielding material.
Lead has high atomic number and high density.
Hence it absorbs X-rays effectively due to photoelectric effect.
Step 3: Therefore protection used.
Radiographers wear lead aprons.
Final Answer:

Step 1: Understand the reagents.
- NaBH reduces the aldehyde group to a primary alcohol. - Pb is involved in the formation of a reaction intermediate. - Mg/ether helps in Grignard reagent formation. - CO /H O introduces a carboxyl group, forming a carboxylic acid.

Step 2: Final product.
The final product after these reactions is COOH (carboxylic acid).

Step 1: Understanding Lassaigne’s Test for Nitrogen
Lassaigne’s test is used to detect the presence of nitrogen in organic compounds.
The compound is fused with sodium metal, and the resulting mixture is tested for the presence of cyanide ions ( ).
Step 2: Analyzing the Given Compounds
(A) Urea: Contains nitrogen and will show a positive Lassaigne’s test.
(B) Hydrazine: Does not contain carbon, so it cannot form sodium cyanide ( ) and does not show a positive Lassaigne’s test.
(C) Phenylhydrazine: Contains nitrogen and will show a positive Lassaigne’s test.
(D) Azobenzene: Contains nitrogen in the form of an azo group ( ), which does not produce cyanide ions during Lassaigne’s test but may give a weak or false-positive result.
Step 3: Determining the Correct Answer
Since hydrazine ( ) does not contain carbon, it does not form sodium cyanide upon reaction with sodium metal and therefore does not give a positive Lassaigne’s test. Final Answer: Hydrazine does not show Lassaigne’s test for nitrogen.