Chemistry — Part 2 MCQs with Explanations

Copper was first used by man over 10,000 years ago. A copper pendant discovered in what is now northern Iraq has been dated about 8700 B.C. For nearly five millennia copper was the only metal known to man, and thus had all the metal applications.

In chemistry, hydronium is the common name for the aqueous cation H 3O+ , the type of oxonium ion produced by protonation of water.

Cesium(Cs) is the most electropositive element.

Permanent hardness of water cannot be removed by simple physical methods like boiling, filtering and distillation.

0.01 minute is the most dangerous to handle.

Ethylene gas, acetylene gas liberated from calcium carbide, and ethephon are some of the commercial ripening agents used successfully in the trade and they have been widely studied for their effectiveness on initiating and accelerating the ripening process and their effect on fruit quality and health related issues. Green fruits are ripened by ethylene gas.

Zone refining is a very useful method to get metals with very high purity such as silicon and germanium. It is also referred to as zone melting, floating zone process, and travelling melting zone.

The main chemical constituent of the oil of cardamom which is responsible for flavour of this oil is cineole.

HF has the highest percentage of ionic character because F has the greatest electronegativity. F, Cl, I, and Br are all in the same group so that means their electronegativity (and thus percentage of ionic character) decreases as they go down the group in the periodic table.

The high reactivity of fluorine is due to its high electronegativity.

The iron ore magnetite consists of Fe 2 O 3 .

The ionisation energy for the hydrogen atom can be written as: Ionisation energy = energy in first orbit - energy in infinite orbit Ionisation energy = ​ E = -E 0 / n 2 , where E 0 = 13.6 eV (1 eV = 1.602×10 -19 Joules) and n = 1,2,3… and so on. The difference in energy = Einfinity - E1 so the ionisation energy from the ground state = x KJ = 0-( -E 0 /1 2 ) = E 0 The energy required to jump the elctron from second to the third stage is:

Below a height of about 86 kilometers, the three main gaseous elements, which together account for about 99.9% of the total atmosphere, exist in essentially constant proportion to the total: nitrogen comprises 78% of air by volume, oxygen comprises 21% of air by volume, and argon comprises another 0.9%.

Aluminium silicate is the main Chemical constituent of clay.

The mineral containing both magnesium and calcium is Dolomite.

The metal does not give H2 on treatment with dilute HCL is Ag.

In this question gram molecules simply means number of moles of O 2 molecules. So we have 6.02*10^24 atoms of Oxygen means 3.01*10^24 molecules of O 2 . 3.01*10^24 molecules of O 2 are equal to 5 moles . Source : Quora.com

The most extensive, commercially useful source of thorium as monazite sand occurs in India at Travancore coast.

Caffeine is the main active constituent of tea and coffee.

The maximum number of isomers for an alkene with molecular formula C 4 H 8 is 4.

The allotropes of carbon include graphite, one of the softest known substances, and diamond, the hardest naturally occurring substance.

Bauxite is the most common aluminum ore.

The organic reaction represented by equation CH 3 - CH = O + H 2 NOH gives CH 3 - CH - NH + H 2 O is an example of a condensation reaction.

H+ is a hydrogen ion, and it is an ion because it LOST an electron. Electrons are negatively charged. When an atom gains electrons it will have NEGATIVE charges. So it has zero electron.

The hottest part of the gas flame is known as luminous zone.

The human body is made up of several chemical elements; the element present in the highest proportion (65%) in the body is Oxygen.

The isomerism which exists between CH 3 CHCI 2 and CH 2 CI. CH 2 CI is positional isomerism.

The half life period of an isotope is 2 hours. After 6 hours 1/8 of the original amount, or 12.5% of the isotope will be left behind.

The number of waves made by an electron moving in an orbit having maximum magnetic quantum number is +3 is 4.

The number of atoms present in 21.6 gram of silver (atomic weight = 108) are same as the molecules in 12 moles of KMnO 4 .

National Chemical Laboratory (CSIR-NCL), Pune, established in 1950, is a constituent laboratory of Council of Scientific and Industrial Research (CSIR).

Convert the mass into moles ( use the formula n=m/Mr ) m = mass and Mr = Molecular weights Molecular weights are 32( Oxygen ), 2( Hydrogen ), and 16( Methane ), respectively. Since the masses are equal, you can take the mass as x. So, the number of moles would be: n(O2) = x/32 n(H2) = x/2 n(CH4) = x/16 The ratio of their volumes is (O 2 ) : (H 2 ) : (CH 4 ) = 1 : 16 : 2

The mass number of an atom is equal to the number of nucleons.

Covalency of an atom in a covalent compound is the number of covalent bonds formed by an atom. Maximum covalency of Nitrogen is 4 (example - ammonium ions).

The formula C 6 H 5 -CO-CH 3 represents Acetophenone.

In the US, 63% of magnesium production came from seawater and brines during 2015. The metal is extracted from seawater and brines by means of electrolysis, a process that requires the passing of a current through a molten salt.

Levigation is based on the difference in densities of the metallic ore and gangue particles. Powdered ore is treated with a stream of running water when the lighter gangue particles are washed away and heavier ore particles are left behind.

The inert gases are sparingly soluble in water.

The molecular formula of phosphorous is P 4 .

They are associated with the development of periodic table of elements. Newland gave the Newland's law of octaves. Mendeleev gave the period law based on atomic mass. Moseley gave the modern period law based on atomic number.