Chemistry MCQ Questions with Answer for all Competitive Exams

Explanation: Chlorophyll is a green pigment in which at the centre of the ring is a magnesium ion. It also bears a long phytol chain.

Explanation: Cracking is the process whereby complex organic molecules such as kerosene or heavy hydrocarbons are broken down into simpler molecules such as light hydrocarbons, by the breaking of carbon-carbon bonds.

Smelting is a form of extractive metallurgy; its main use is to produce a metal from its ore. In this process the oxide ore is reduced to free metal by using reducing agents like coke or charcoal. Copper is also obtained from its oxide by this method in Free State.

Hydrogenation is a reduction reaction which results in an addition of hydrogen (usually as H₂). If an organic compound is hydrogenated, it becomes more ‘saturated’. Hydrogenation results in the conversion of liquid vegetable oils to solid (edible) fats.

Vulcanization is a chemical process for converting rubber into more durable materials via the addition of sulfur. Sulfur modifies the rubber by forming cross-links (bridges) between individual polymer chains. Vulcanized material is less sticky and has superior mechanical properties.

Explanation: Helium gas is lighter than air and non-flammable (non-combustible) so it is used in balloons.

Explanation: Ethylene Glycol is used to prevent the freezing of fuel in space crafts.

Explanation: The tracking of people by trained dogs is based on the recognition of carboxylic acid in sweat from feet.

Explanation: The addition of silicates to synthetic detergents has proved very beneficial. Silicates soften water by the formation of precipitates that can be easily rinsed away. Soluble silicates contribute to detergents as cleaning aids, processing aids, and corrosion inhibitors. As for cleaning aids, soluble silicates provide alkalinity and promote soil suspension. Sodium sulfate is simply a filler in detergent powder, in much the same way as fillers are used in many medical tablets, it doesn’t play an active role as such.

Explanation: Methyl Alcohol or Methanol (CH₃OH) is known as wood spirit. It is also known as wood alcohol because it was formerly obtained by the destructive distillation of wood.

Explanation: ​​In the reactivity series of metals, copper is placed below the hydrogen. Hence, it is less reactive than hydrogen. On the other hand barium, lead and magnesium are placed above the hydrogen hence, these are more reactive than hydrogen.

Explanation: Saponification is the alkaline hydrolysis of the fatty acid esters. Example: The chemical reaction between fatty acid and sodium hydroxide is a saponification reaction.

Triglyceride + Sodium hydroxide → Glycerol + 3 soap molecules.

Explanation: C₁₁-L-methyl-methionine is used in position emission tomography (PET) to locate and differentiate primary brain tumours and also to monitor the therapeutic effect of tumour irradiation.

Explanation: Liquefied Natural Gas or LNG is natural gas (predominantly methane, CH₄) that has been converted temporarily to liquid form for ease of storage or transport. The liquefaction process involves the removal of certain components, such as dust, acid gases, helium, water, and heavy hydrocarbons, which could cause difficulty downstream. The natural gas is then condensed into a liquid maximum transport pressure set at around 25 kPa/3.6 psi by cooling it to approximately –162 °C (–260 °F). Dahej, in India, has begun its first import of natural gas.

Natural gas liquids recovery (NGL) involves refrigerated gas plants, turboexpanders, and debutanizers, depropanizers, and JT plants. NGL can be separated using debutanizers and depropanizers into propane, butane, naphtha, etc.

Explanation: Car and other automobiles exhaust mainly contains CO, lead and SO₂ and out of these CO is the most toxic.

Explanation: RDX, an initialism for Research Department Explosive, is an explosive nitroamine widely used in military and industrial applications. It is also known less commonly as cyclonite. Its chemical name is cyclotrimethylene trimipramine.

Explanation: Sundarlal Bahuguna coined the Chipko slogan “Ecology is Permanent Economy”. The first chipko action took place spontaneously in April 1973 in the village of Mandal in the Upper Alaknanda Valley and over the next five years spread to many districts of the Himalayas in Uttarakhand.

Explanation: Alum stops bleeding in a minor cut. Its chemical name is potassium aluminium sulfate. It stops bleeding because of coagulation. Blood is a colloid of proteins in water and the K⁺, Al^3+, and SO₄^– ions coagulate them, causing a blood clot.

Explanation: Water pollution in the river or any other water body is measured by the amount of dissolved oxygen. Water pollution can be measured on the basis of parameters like dirtiness, change in texture, total suspended solids, and other important factors like,

1. A decrease in dissolved oxygen (DO) (concentration of dissolved oxygen in water samples).
2. An increase in BOD, (Biochemical Oxygen Demand) is a chemical procedure for determining the amount of dissolved oxygen needed by aerobic biological organisms in a body of water to break down organic material present in a given water sample at a certain temperature over a specific time period.
3. An increase in COD, (Chemical Oxygen Demand) test is commonly used to indirectly measure the number of organic compounds in water.

Explanation: Solders are typically made from tin or lead or a combination of both in the

Explanation: All noble gases are present in Earth’s atmosphere except for helium and radon. Noble gases are a group of highly unreactive elements placed in the Gr-18 (VIIIB) in the periodic table.

Explanation: Atomic size is of the order of 10 ^–10 m or 10 ^–8 cm. Atomic size is the distance from the nucleus to the Valence Shell (outermost shell) of an atom.

Explanation: The different types of radiations are arranged in the decreasing order of frequencies or increasing order of wavelength as Cosmic rays, Gamma rays, X-rays, Ultraviolet radiations, visible radiations, Infrared radiations, Microwaves, and Radio waves.

Explanation: Atoms of an element having the same atomic number but having different mass numbers are known as isotopes. e.g. 1H¹, 1H², 1H³

Explanation: Ni-Cd batteries contain nickel hydroxide as a positive electrode plate, a cadmium hydroxide as a negative electrode plate, and an alkaline electrolyte as a separator. The chemical reaction which occurs in Ni-Cd battery is

2NiO(OH) + Cd + 2HO₂ ↔ Ni(OH) + Cd(OH)

Explanation: Ammonia is used as a large-scale refrigerant because it has the highest refrigerating capacity per pound of any refrigerant and a number of other excellent thermal properties that make it popular for a number of refrigeration applications in spite of its being toxic, explosive, and flammable within certain conditions. Ammonia is used as a refrigerant prominently in the refrigeration systems of the food industry like dairies, ice creams plants, frozen food production plants, cold storage warehouses, processors of fish, meat, and a number of other applications. Comparatively chlorofluorocarbon (CFC) chemical, safer refrigerators were possible for home and consumer use.

Explanation: According to the Aufbau principle in the ground state of the atoms, the orbitals are filled in order of their increasing order of energy.

Explanation: Radioactivity was discovered by Henri Becquerel (1895-96). For work in this field he, along with Marie Sklodowska-Curie and Pierre Curie, received the 1903 Nobel Prize in Physics.