Chemistry MCQs

Notes:
John Dalton introduced the atomic theory into chemistry. The main points of Dalton’s atomic theory are (1) Elements are made of extremely small particles called atoms. (2) Atoms of a given element are identical in size, mass and other properties; atoms of different elements differ in size, mass and other properties.(3) Atoms cannot be subdivided, created or destroyed. (4) Atoms of different elements combine in simple whole-number ratios to form chemical compounds. (5) In chemical reactions, atoms are combined, separated or rearranged.

Notes:
Tartaric acid occurs naturally in many fruits such as grapes, bananas, tamarinds, and citrus. Its salt, potassium bitartrate, commonly known as cream of tartar, develops naturally in the process of winemaking. It is commonly mixed with sodium bicarbonate and is sold as baking powder used as a leavening agent in food preparation. The acid itself is added to foods as an antioxidant E334 and to impart its distinctive sour taste.

Notes:
The reaction of alkali metals with water produces Hydrogen gas. These metals are part of the first group on the period table and include lithium, sodium, and potassium. They are known for their vigorous reactions with water, which results in the liberation of hydrogen gas. Along with the gas, this reaction also forms a basic alkali metal hydroxide, which gives the solution its characteristic basic or alkaline properties.

Notes:
Vapor pressure of water increases as its temperature rises. At 25°C, water’s vapor pressure is approximately 23.8 mmHg, while at 100°C it reaches 760 mmHg. When a liquid is heated, kinetic energy of molecules grows, allowing more to escape as vapor and thus increasing vapor pressure.

Notes:
The main constituent of vegetable oil and animal fats is triglyceride. Triglycerides are composed of three fatty acids linked to a glycerol molecule. They are the most common type of fat found in the body and serve as a major energy source. In fact, triglycerides account for about 95% of the fats in the human diet.

Notes:
Carbamide is another name of Urea, an organic compound with chemical formula CO(NH₂)₂. This name indicates that Urea is an amide in which two –NH₂ groups are joined by a carbonyl (C=O) functional group.

Notes:
Iodine-135 is a important by-product of nuclear fission, particularly in reactors using uranium fuel. It has a high neutron capture cross-section, meaning it effectively absorbs neutrons, which can inhibit the fission process and reduce reactor power output. This property makes it crucial for managing reactor control and safety, as its presence can lead to a phenomenon known as “neutron poison,” affecting the overall efficiency of the nuclear reaction.

Notes:
The correct answer is Aryl. In organic chemistry, when a hydrogen atom is removed from a benzene ring (a hydrocarbon), the remaining structure is referred to as an aryl group. Aryl groups are derived from aromatic compounds, specifically those containing a benzene ring. For example, when a hydrogen is removed from toluene (methylbenzene), the resulting aryl group is called a tolyl group. Aryl groups are important in various chemical reactions and are foundational in the synthesis of many organic compounds.

Notes:
The correct composition of biogas released through anaerobic bio-digester system is:
Methane (CH4) – 50–75 %
Carbon dioxide (CO2) – 25–50%
Nitrogen (N2) – 0–10%
Hydrogen (H2) – 0–1%
Hydrogen sulphide (H2S) – 0–3%

Notes:
Strontium-90 is a “bone seeker” that exhibits biochemical behaviour similar to calcium, the next lighter Group 2 element. After entering the organism, most often by ingestion with contaminated food or water, about 70–80% of the dose gets excreted. Virtually all remaining strontium-90 is deposited in bones and bone marrow, with the remaining 1% remaining in blood and soft tissues. Its presence in bones can cause bone cancer, cancer of nearby tissues, and leukaemia.