Chemistry MCQs

Notes:
Bakelite is a thermosetting plastic formed from phenol and formaldehyde, used in electrical insulators and cookware handles. Unlike thermoplastics, it hardens irreversibly when heated and cannot be remolded. It was the first synthetic plastic, invented by Leo Baekeland in 1907.

Notes:
Silver is the metal with the highest electrical and thermal conductivity. It has only one valence electron, which can move around with little resistance. This makes silver a great conductor of electricity and heat.
Silver’s thermal conductivity is 430 wK/m, which is higher than copper (400 wK/m), aluminum (235 wK/m), and brass (109 wK/m).
Silver’s low contact wear resistance and excellent optical reflectivity make it ideal for coating contacts, mirrors, and conductors in telecom applications.
Impurities can decrease a conductor’s conductivity. For example, sterling silver is not as good of a conductor as pure silver. Oxidized silver is not as good a conductor as untarnished silver.

Notes:
Platinum is a naturally white metal. It doses not need to be alloyed for color. Due to its appearance as white, it is commonly known as White Gold.

Notes:
Cellulose is the most abundant organic compound in nature. It is the main constituent of plant fiber. Plants contain on average 33% cellulose, and cotton is the purest form at 90%. Chitin is the second most abundant organic compound in nature.

Notes:
Hydrogen (H2) gas is utilized in the manufacture of Vanaspati ghee from vegetable oils. The process involves hydrogenation, a chemical reaction between molecular hydrogen (H2) and another compound or element. Hydrogenation of vegetable oils helps to convert them into a semisolid form that resembles ghee, often used as a cheaper alternative to butter or ghee in cooking.

Notes:
Alcohols are organic compounds characterized by the presence of a hydroxyl group, denoted as -OH. This group consists of one oxygen atom bonded to a hydrogen atom. Due to the presence of the hydroxyl group, alcohols exhibit unique properties, such as the ability to form hydrogen bonds, making them polar. Alcohols are distinct from carboxylic acids (COOH), carbonates (COO), and carbonyl group compounds (CO).

Notes:
The electric heating is also used to produce light, as in an electric bulb. Here, the filament must retain as much of the heat generated as is possible, so that it gets very hot and emits light. It must not melt at such high temperature. A strong metal with high melting point such as tungsten (melting point 3380°C) is used for making bulb filaments. The filament should be thermally isolated as much as possible, using insulating support, etc. The bulbs are usually filled with chemically inactive nitrogen and argon gases to prolong the life of filament. Most of the power consumed by the filament appears as heat, but a small part of it is in the form of light radiated.

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:
Alkaloids are a class of naturally occurring organic compounds that mostly contain basic nitrogen atoms. Nitrogen is essential in their structure, contributing to their pharmacological properties. Common examples of alkaloids include morphine, caffeine, and nicotine, all of which contain nitrogen. Sodium, magnesium, and potassium are not fundamental components of alkaloids.

Notes:
The Haber Process is an industrial method for synthesizing ammonia from nitrogen and hydrogen gases. Developed by Fritz Haber and Carl Bosch in the early 20th century, it operates under high pressure and temperature, using an iron catalyst. Ammonia produced is crucial for fertilizers, supporting global agriculture. The process importantly increased food production, earning Haber the Nobel Prize in Chemistry in 1918.