General Chemistry

Step 1: Paramagnetic nature.
The compounds of transition elements show paramagnetism due to the presence of one or more unpaired electrons in their (n−1)d orbitals.
The magnetic moment ( ) of such compounds is given by: where = number of unpaired electrons.
Step 2: Explanation.
- When an element or its ion has unpaired electrons, it is attracted by a magnetic field (paramagnetic).
- If all electrons are paired, the substance becomes diamagnetic.
Step 3: Examples.
- Fe : [Ar] 3d → 4 unpaired electrons → paramagnetic.
- Zn : [Ar] 3d → all paired → diamagnetic.
Step 4: Coloured nature.
Transition metal compounds are coloured due to the presence of incompletely filled d-orbitals.
When light falls on these compounds, electrons in the d-orbitals absorb specific wavelengths of light and jump from lower energy levels to higher ones (known as d–d transitions). The remaining transmitted light imparts colour.
Step 5: Examples.
- [Ti(H O) ] is purple due to d–d transition.
- [Cu(H O) ] is blue due to the absorption of red light.
Step 6: Conclusion.
Hence, the presence of unpaired d-electrons makes transition metal compounds both paramagnetic and coloured.

Step 1: Definition.
Preservatives are chemical substances added to food, drugs, cosmetics or other perishable materials to prevent spoilage caused by microbes (bacteria, fungi) or by chemical changes such as oxidation.
Step 2: How they work.
They either (i) inhibit microbial growth, (ii) kill microorganisms, or (iii) slow oxidation and rancidity.
Step 3: Common examples.
- Antimicrobial: sodium benzoate, benzoic acid, potassium metabisulphite (K S O ), sodium nitrite (meats).
- Antioxidant: BHA (butylated hydroxyanisole), BHT (butylated hydroxytoluene), ascorbic acid.
Step 4: Conclusion.
Thus, preservatives extend shelf life and maintain safety/quality of products by preventing microbial and oxidative deterioration.

Step 1: Concept.
Insulin is a hormone secreted by the beta cells of the Islets of Langerhans in the pancreas. It regulates glucose metabolism.
Step 2: Analysis of options.
(A) Thyroid: Secretes thyroxine, not insulin.
(B) Pancreas: Correct, insulin is secreted here.
(C) Adrenal body: Secretes adrenaline, not insulin.
(D) None of these: Incorrect.
Step 3: Conclusion.
Thus, insulin is secreted by the pancreas, so the correct answer is (B).

Step 1: Concept.
Cellulose is the most abundant carbohydrate on Earth. It is the structural component of plant cell walls.
Step 2: Analysis of options.
(A) Glucose: It is very common but not the most abundant polymer in nature.
(B) Fructose: A fruit sugar, less abundant overall.
(C) Starch: A storage carbohydrate, but not as abundant as cellulose globally.
(D) Cellulose: Correct, makes up plant biomass and is the most abundant carbohydrate.
Step 3: Conclusion.
Thus, the correct answer is (D) Cellulose.

Step 1: Definition.
Lactose is the disaccharide sugar naturally found in milk and dairy products. It is composed of glucose + galactose.
Step 2: Analysis of options.
(A) Sucrose: Common sugar, found in sugarcane and beetroot, not in milk.
(B) Lactose: Correct — main sugar in milk.
(C) Maltose: Present in germinating grains, not in milk.
(D) None of these: Incorrect.
Step 3: Conclusion.
Hence, the correct answer is (B) Lactose.