31. Consider the following:
- Clay
- Milk
- Blood
- Urea
Which of the above is/are classified as colloids?
[A] Only 1, 2 & 3
[B] Only 1 & 4
[C] Only 2, 3 and 4
[D] 1, 2, 3 and 4
Show Answer
Correct Answer: A [Only 1, 2 & 3]
Notes:
- Clay, milk, and blood are all colloids, consisting of small particles dispersed in a liquid.
- Clay transitions from a liquid to a solid state, affecting its crack formation.
- Milk’s colloidal structure influences its properties, and crack patterns can indicate quality.
- Blood’s cellular composition leads to unique drying patterns, which can help diagnose health conditions.
- All three materials exhibit similar mechanical behaviors when drying, making them relevant for studies on crack formation.
- Urea, however, is a true solution when dissolved in water, as its molecules completely dissolve and do not form a colloidal system.
32. Consider the following scientists and their contributions:
- J.J. Thomson – Discovery of the electron
- James Chadwick – Discovery of the neutron
- Ernest Rutherford – Discovery of the nucleus through gold foil experiment
How many of the above are correctly matched?
[A] Only 1
[B] 1 and 2 only
[C] 1, 2, and 3
[D] 2 and 3 only
Show Answer
Correct Answer: C [1, 2, and 3]
Notes:
All three scientists are correctly matched with their discoveries. J.J. Thomson discovered the electron in 1897. Ernest Rutherford identified the nucleus through the gold foil experiment in 1911. James Chadwick discovered the neutron in 1932. These breakthroughs formed the foundational understanding of atomic structure in modern science.
33. Who used X-ray crystallography to provide evidence for DNA structure?
[A] Francis Crick
[B] James Watson
[C] Rosalind Franklin
[D] Linus Pauling
Show Answer
Correct Answer: C [Rosalind Franklin]
Notes:
Rosalind Franklin used X-ray crystallography to capture Photograph 51, revealing DNA’s helical structure. Her data were vital for Watson and Crick’s double helix model. Although she did not receive the Nobel Prize, Franklin’s contributions are foundational in molecular biology.
34. With reference to acids, consider the following:
- Sulphuric acid
- Nitric acid
- Hydrochloric acid
- Acetic acid
How many of the above are classified as mineral acids?
[A] 2 only
[B] 1 only
[C] 4
[D] 3 only
Show Answer
Correct Answer: D [3 only]
Notes:
Sulphuric acid, Nitric acid, and Hydrochloric acid are mineral acids because they are inorganic acids derived from minerals. Acetic acid, in contrast, is an organic acid found in vinegar. Therefore, only three out of the four acids listed are classified as mineral acids.
35. Consider the following elements:
- Silicon
- Germanium
- Gallium
Which of the above are used in the chip making industry?
[A] Only 1 and 2
[B] Only 1 and 3
[C] Only 2 and 3
[D] 1, 2 and 3
Show Answer
Correct Answer: D [1, 2 and 3]
Notes:
All three elements — silicon, germanium, and gallium — are used in the semiconductor industry. Silicon is the most widely used, but germanium is found in transistors and fiber optics, while gallium is vital in compounds like gallium arsenide and gallium nitride, important for advanced electronic and optoelectronic applications.
36. How many of the following substances are commonly used as bleaching agents?
- Sulphur dioxide
- Chlorine
- Ozone
- Ammonia
Select the correct option from the codes given below:
[A] Only one
[B] Only two
[C] Only three
[D] All Four
Show Answer
Correct Answer: C [Only three ]
Notes:
Sulphur dioxide, chlorine, and ozone are commonly used as bleaching agents: sulphur dioxide for delicate fibers, chlorine in paper and textiles, and ozone for cold bleaching. Ammonia is not a bleaching agent; it is primarily used in fertilizers and cleaning products. Therefore, only 3 out of the 4 substances listed are bleaching agents.
37. Which of the following pairs of substances share a common characteristic?
- Diamond and Silicon carbide
- Graphite and Copper
- Sodium chloride and Quartz
- Teflon and Polythene
Select the correct option from the codes given below:
[A] 1, 2 and 4 only
[B] 1 and 3 only
[C] 2 and 4 only
[D] 1, 2, 3 and 4
Show Answer
Correct Answer: A [1, 2 and 4 only]
Notes:
Diamond and silicon carbide are both hard covalent-network solids. Graphite and copper both conduct electricity due to free electrons. Teflon and polythene are non-polar, hydrophobic polymers. Sodium chloride is ionic, whereas quartz is a covalent network solid, so they do not share a common crystal characteristic.
38. Which is the rarest and most expensive naturally occurring precious metal?
[A] Rhodium
[B] Platinum
[C] Gold
[D] Palladium
Show Answer
Correct Answer: A [Rhodium]
Notes:
Rhodium is the rarest and most valuable precious metal, primarily used in catalytic converters and jewelry. It is rarer than gold and platinum, highly reflective, corrosion-resistant, discovered by William Hyde Wollaston in 1803, and has the chemical symbol Rh with atomic number 45.
39. Which metal forms a transparent thin film for touchscreen use?
[A] Tantalum
[B] Zirconium
[C] Indium
[D] Hafnium
Show Answer
Correct Answer: C [Indium]
Notes:
Indium, when alloyed with tin, produces indium tin oxide (ITO). ITO is a transparent and electrically conductive thin film essential for touchscreens, LCDs, and solar panels. Other options have applications in electronics or industry, but only indium forms this crucial transparent conductive layer.
40. Which element has negative thermal expansion in some crystalline phases?
[A] Beryllium oxide
[B] Palladium
[C] Tungsten carbide
[D] Zirconium tungstate
Show Answer
Correct Answer: D [Zirconium tungstate]
Notes:
Zirconium tungstate (ZrW₂O₈) contracts when heated over a wide temperature range, exhibiting negative thermal expansion due to its open framework structure and transverse vibrational modes. This rare property is used in precision optics and composite materials requiring controlled expansion.
