15 previous year UPSC Prelims questions on physical chemistry are on this page, from 1996 to 2009. UPSC asks about the order of filling of orbitals, the magnetic quantum number, half-life, radioactive elements, the dry cell and glass that cuts ultraviolet rays. The explanations focus on the principle rather than on equations.
Explanations state facts as of the year each question was asked; words like “recently” refer to that year.
Showing 11–15 of 15 questions
Barium is used in X-ray imaging because it effectively absorbs X-rays, which makes it show up clearly on X-ray images. This property helps in creating a clear contrast between the stomach and surrounding tissues, allowing doctors to examine the stomach’s structure more easily.
Cobalt-60 is a radioactive isotope that emits gamma rays. These high-energy rays are used in radiation therapy for cancer treatment because they can penetrate deep into tissues and target cancer cells effectively while minimizing damage to surrounding healthy tissues. Related terms:
Proton therapy is a type of cancer treatment that uses protons to precisely target and destroy tumor cells, minimizing damage to surrounding healthy tissues. It is particularly effective for tumors near sensitive areas, offering fewer side effects compared to conventional radiation therapy.
| List-I | List-II |
|---|---|
| A. Dr. Raja Ramanna | 1. Plant chemistry |
| B. Dr. M.S. Swaminathan | 2. Nuclear physics |
| C. Prof. U.R Rao | 3. Thermodynamics & astrophysics |
| D. Prof. Meghnad Saha | 4. Space research |
| 5. Agricultural science |
A is matched with 2: Dr. Raja Ramanna was a distinguished Indian physicist best known for his role in the development of India’s nuclear program, including the Pokhran-I nuclear test in 1974. B is matched with 5: Dr. Swaminathan is renowned for his contributions to the Green Revolution in India, which transformed the country into a self-sufficient food producer. His focus on developing high-yield and disease-resistant crop varieties, combined with sustainable agricultural practices, earned him global recognition in agricultural science. C is matched with 4: Prof. Udupi Ramachandra Rao was a visionary space scientist who led the design and launch of India’s first satellite, Aryabhata, in 1975. Also as the chairman of ISRO, he contributed significantly to advancing India’s space program. D is matched with 3: Prof. Meghnad Saha is celebrated for the Saha Ionization Equation, which explains the physical and chemical conditions in stars. He also made notable contributions to thermodynamics.
Zirconium is an essential element for the construction of nuclear reactors due to its unique properties:
Low Neutron Absorption: Zirconium has a low neutron absorption cross-section, making it ideal for use in nuclear reactors as it does not interfere significantly with the nuclear chain reaction. High Corrosion Resistance: It is resistant to corrosion in the presence of coolant water, including high-temperature water, which is commonly used in nuclear reactors. Strength and Durability: Zirconium alloys are strong and durable, making them suitable for structural components like cladding for fuel rods. This combination of properties makes zirconium critical in the nuclear industry.
An alpha particle consists of two protons and two neutrons, which is exactly the nucleus of a helium atom (He2+). The mass of an alpha particle is very close to the mass of a helium atom as the mass of electrons is insignificant in comparison with protons and neutrons.
| Q | UPSC year | Correct answer |
|---|---|---|
| 11 | 1999 | (c) barium is a good absorber of X-rays and this helps the stomach to appear clearly in contrast with the other regions in the picture. |
| 12 | 1999 | (c) Gamma rays |
| 13 | 1998 | (c) A-2; B-5; C-4; D-3 |
| 14 | 1998 | (c) Zirconium |
| 15 | 1996 | (b) an atom of helium |
This page covers 15 previous year UPSC Prelims GS Paper-I questions on Chemistry: Physical Chemistry (Science and Technology), asked from 1996 to 2009. Each has the correct answer and an explanation.
Electrons fill the lowest-energy orbitals first before moving to higher ones. It governs the order in which orbitals are filled in an atom and so explains the arrangement of electrons.
One-fourth. After one half-life, half remains; after the second, half of that remains. With a half-life of four months, three-fourths of the substance has therefore decayed in eight months.
