Chemistry Solved MCQs


What is "milk of magnesia" chemically?

A. Magnesium carbonate
B. Sodium bicarbonate
C. Calcium hydroxide
D. Magnesium hydroxide
Answer» D. Magnesium hydroxide
Explanation: agnesium hydroxide is an inorganic compound with the chemical formula Mg(OH)2. As a suspension in water, it is often called milk of magnesia because of its milk-like appearance. The solid mineral form of magnesium hydroxide is known as brucite.

Milk tastes sour when kept in the open for sometime due to the formation of –

A. lactic acid
B. citric acid
C. acetic acid
D. carbonic acid
Answer» A. lactic acid
Explanation: Like many other things, milk contains bacteria, Milk also naturally contains a kind of sugar known as "lactose." The bacteria that live in milk get energy from this special sugar and use it to reproduce to make even more bacteria. When the bacteria use the lactose sugars to reproduce, they change it from "lactose sugar" into "lactic acid," which tastes sour.

Which of the following is a natural dye?

A. Crystal violet
B. Aniline blue
C. Alizarin
D. Phenolphthalein
Answer» C. Alizarin
Explanation: Alizarin or 1,2- dihydroxyanthraquinone (also known as Mordant Red 11 and Turkey Red is an organic compound with formula C14H8O4 that has been used throughout history as a prominent red dye, principally for dyeing textile fabrics. Historically it was derived from the roots of plants of the madder genus. In 1869, it became the first natural pigment to be duplicated synthetically.

The ratio of pure gold in 18 carat gold is

A. 60%
B. 75%
C. 80%
D. 90%
Answer» B. 75%
Explanation: There are various grades of gold purity, determined by the ratio of their alloy composition and rated by a karat system. Typical karat purities range from 10 karats to 24 karats (pure gold), with a wide variation of usage from country to country, 18 karat gold consists of 75% gold and 25% alloy metals. 18 karat gold has been found to be the perfect balance between gold purity and strength. Brilliance offers a variety of exquisite 18 karat gold jewelry.

               is the process in which acids and bases react to form salts and water.

A. Neutralization
B. Electrolysis
C. Distillation
D. Hydrolysis
Answer» A. Neutralization
Explanation: Neutralization is a process when acids and bases react to form salt and water.

The gas usually causing explosions in coal mines is –

A. Hydrogen
B. Carbon monoxide
C. Air
D. Methane
Answer» D. Methane
Explanation: Firedamp is flammable gas found in coal mines. It is the name given to a number of flammable gases, especially methane.

Which is the purest form of iron?

A. Steel
B. Cast iron
C. Pig iron
D. Wrought iron
Answer» D. Wrought iron
Explanation: Iron is a chemical element with the symbol Fe and atomic number 26. It is a metal in the first transition series. It is the most common element (by mass) forming the planet Earth as a whole, forming much of Earth's outer and inner core. It is the fourth most common element in the Earth's crust. Wrought iron is the purest form of iron. It contains less than 0.25% carbon.

Which of the following metals form an amalgam with other metals?

A. Lead
B. Tin
C. Zinc
D. Mercury
Answer» D. Mercury
Explanation: An amalgam is a substance formed by the reaction of mercury with another metal. Almost all metals can form amalgams with mercury, notable exception being iron. Silver-mercury amalgams are important in dentistry, and gold-mercury amalgam is used in the extraction of gold from ore. Dentistry has used alloys of mercury with metals such as silver, copper, indium, tin and zinc. Amalgam is an "excellent and versatile restorative material" and is used in dentistry for a number of reasons.

Petroleum is a mixture of –

A. elements
B. hydrocarbons
C. polymers
D. salts
Answer» B. hydrocarbons
Explanation: Petroleum or crude oil is a naturally occurring flammable liquid consisting of a complex mixture of hydrocarbons of various molecular weights and other liquid organic compounds, that are found in geologic formations beneath the Earth's surface. A fossil fuel, it is formed when large quantities of dead organisms, usually zooplankton and algae, are buried underneath sedimentary rock and undergo intense heat and pressure.

The gas used for filling weather balloons is –

A. helium
B. hydrogen
C. air
D. nitrogen
Answer» A. helium
Explanation: A balloon is an inflatable flexible bag filled with a gas, such as helium, hydrogen, nitrous oxide, oxygen, or air. Modern balloons can be made from materials such as rubber, latex, polychloroprene, or a nylon fabric, while some early balloons were made of dried animal bladders, such as the pig bladder. Some balloons are used for decorative purposes, while others are used for practical purposes such as meteorology, medical treatment, military defense, or transportation.

An emulsion is a colloid of a –

A. gas in a liquid
B. liquid in a liquid
C. liquid in a gas
D. gas in a solid
Answer» B. liquid in a liquid
Explanation: An emulsion is a mixture of two or more liquids that are normally immiscible (nonmixable or unblendable). Emulsions arepart of a more general class of two-phase systems of matter called colloids. Although the terms colloid and emulsion are sometimes used interchangeably, emulsion should be used when both the dispersed and the continuous phase are liquids. In an emulsion, one liquid (the dispersed phase) is dispersed in the other (the continuous phase). Examples of emulsions include vinaigrettes, milk, mayonnaise, and some cutting fluids for metal working.

Percentage of carbon in steel ranges from –

A. 0.1 to 1.5
B. 1.5 to 3.0
C. 3.0 to 4.0
D. 4.0 to 6.0
Answer» A. 0.1 to 1.5
Explanation: Steel is an alloy made by combining iron and other elements, the most common of these being carbon. When carbon is used, its content in the steel is between 0.2% and 2. 1% by weight, depending on the grade. Other alloying elements sometimes used are manganese, chromium, vanadium and tungsten.

Which of the following gases makes bread or cake rise making them soft and spongy?

B. H2
C. CO2
D. O2
Answer» C. CO2
Explanation: Breads rise due to the process of fermentation, a chemical process by which molecules such as glucose are broken down an aerobically.

Candle is a mixture of –

A. Paraffin wax and stearic acid
B. Bees wax and stearic acid
C. Higher fat acids and stearic acid
D. Bees wax and paraffin wax
Answer» A. Paraffin wax and stearic acid
Explanation: The candle can be made of paraffin (a byproduct of petroleum refining), microoystalline wax, stearin (now produced almost exclusively from palm waxes though initially manufactured from animal fats), beeswax (a byproduct of honey collection), gel (a mixture of polymer and mineral oil), some plant waxes (generally palm, carnauba, bayberry, or soybean wax), tallow (rarely used since the introduction of affordable and cheap wax alternatives) or spermaceti (extracted from the head of a Sperm Whale).

German silver, an alloy, does not contain the metal –

A. Nickel
B. Zinc
C. Copper
D. Silver
Answer» D. Silver
Explanation: Nickel silver is a copper alloy with nickel and oft6n. zinc. The usual formulation is 60% copper, 20% nickel and 20% zinc. Nickel silver is named for its silvery appearance, but it contains no elemental silver unless plated. The name "German silver" refers to its development by 19th-century German metalworkers in imitation of the Chinese alloy known as paktong (Cupronickel) All modern, commercially important nickel silvers (such as those standardized under ASTM B 122) contain significant amounts of zinc, and are sometimes considered a subset of brass.

Oxygen which is vital for life is a product of photosynthesis and comes from –

A. carbonates from soil
B. carbon dioxide
C. water
D. oxides of mineral elements
Answer» C. water
Explanation: The unusually high concentration of oxygen has on Earth is the result of the oxygen cycle. This biogeochemical cycle describes the movement of oxygen within and between itsthree main reservoirs on Earth: the atmosphere, the biosphere, and the lithosphere. The main driving factor of the oxygen cycle is photosynthesis, which is responsible for modern Earth's atmosphere. Photosynthesis releases oxygen into the atmosphere, while respiration and decay remove it from the atmosphere.

What is the purpose of adding baking soda to dough?

A. To generate moisture
B. To give a good flavour
C. To give good colour
D. To generate carbon dioxide
Answer» D. To generate carbon dioxide
Explanation: 0

Gobar gas mainly contains –

A. Carbon dioxide
B. Carbon monoxide
C. Hydrogen sulphide
D. Methane
Answer» D. Methane
Explanation: Biogas or Lobar gas is produced by the anaerobic digestion or fermentation of biodegradable materials such as biomass, manure, sewage, municipal waste, green waste, plant material, and crops. It comprises primarily methane (CH4) and carbon dioxide (CO2) and may have small amounts of hydrogen sulphide (H2S), moisture and siloxanes.

The chief constituent of vinegar is –

A. Formic acid
B. Acetic acid
C. Salycylic acid
D. Oxalic acid
Answer» B. Acetic acid
Explanation: Vinegar is a liquid substance consisting mainly of acetic acid (CH3CO2H) and water, the acetic acid being produced through the fermentation of ethanol by acetic acid bacteria. It is today mainly used in the kitchen as a general cooking ingredient, but historically, as the most easily available mildacid, it had a great variety of industrial, medical, and domestic uses.

Commercial Vaseline is derived from -

A. plant gums
B. coal tar
C. wool wax
D. petroleum
Answer» D. petroleum
Explanation: Vaseline is a brand of petroleum jelly based products owned by Anglo-Dutch company Unilever. While Vaseline can be used as a lubricant, it is also a useful moisture insulator for local skin conditions characterized by tissue dehydration. Vaseline helps protect minor cuts and burns.

Colour imparted to the Bunsen flame by strontium salt is -

A. bluish green
B. apple-green
C. brick red
D. crimson red
Answer» D. crimson red
Explanation: A flame test is performed by introducing a sample into the blue flame of a bunsen burner and noting any change in the colour of the flame. The tests can be used to detect the presence of some metallic elements in salts. With strontium salt, the colour of Bunsen flame ranges from crimson to red.

Name the particle that is most essential to continue the chain reaction during the fission of uranium -

A. Electron
B. Proton
C. Neutron
D. Positron
Answer» C. Neutron
Explanation: Nuclear fission is either a nuclear reaction or a radioactive decay process in which the nucleus of an atom splits into smaller parts (lighter nuclei), often producing free neutrons and photons (in the form of gamma rays), and releasing a very large amount of energy, even bythe energetic standards of radioactive decay. Fission as encountered in the modern world is usually a deliberately produced manmade nuclear reaction induced by a neutron.

Which one amongst the following is not a Green House gas?

A. Nitrogen
B. Carbon dioxide
C. Carbon Monoxide
D. Chloro fluoro carbons
Answer» A. Nitrogen
Explanation: A greenhouse has (sometimes abbreviated GHG) is a gas in an atmosphere that absorbs and emits radiation within the thermal infrared range. The primary greenhouse gases in the Earth's atmosphere are water vapour, carbon dioxide, methane, nitrous oxide, and ozone.

The element used in the manufacture of safety matches is –

A. Phosphorous
B. Magnesium
C. Silicon
D. Sulphur
Answer» A. Phosphorous
Explanation: One end of a match is coated with a material that can be ignited by frictional heat generated by striking the match against a suitable surface. The coated end of a match, known as the match "head," contains either phosphorus or phosphorus sesquisulfide as the active ingredient and gelatin as a binder.

The main source of Naphthalene is -

A. Charcoal
B. Camphor
C. Coal-tar
D. Diesel
Answer» C. Coal-tar
Explanation: The main source of Naphthalene is coal-tar. Naphthalene is derived from a kindof naphtha which is a broad term encompassing any volatile, namable liquid hydrocarbon mixture, including coaltar.
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