CHEMISTRY (Part-VI) (Railway)

Butane and 2-methyl propane is an isomeric pair as both consist of 4 atoms of carbon and 10 atoms of hydrogen.

● They have the same molecular formula, i.e., C₄H₁₀.

Group 18 is sometimes called the zero group as its elements have zero valency or their tendency to react is zero.

● The members of this group have eight electrons in their outermost orbit (except helium which has two electrons).

● The members of group 18 are helium (He), neon (Ne), argon (Ar), krypton (Kr), xenon (Xe) and radon (Rn).

● Group 18 element is known as Noble or inert gas. Inert gas don't take participate in physical and chemical reaction.

The correct matches are as follows:

● CH₃COOH: Acetic acid
● CHCl₃: Chloroform
● CH₃CH₂OH: Ethanol
● CH₄: Methane

Valency is based on the outer most shells of the elements.
Halogens belong to group 17 of the periodic table, consisting of highly reactive elements including fluorine, chlorine, bromine etc.

General electronic configuration of halogens is ns² np⁵ that is they have seven electrons in their outermost shell, and they are short of one electron to achieve the nearest noble gas configuration.

So, to achieve their nearest noble gas configuration they have great tendency to accept an electron.

CuSO₄ (aq) + BaCl₂ (aq) → BaSO₄ (s) + CuCl₂ (aq)

● When barium chloride solution is added to copper sulphate solution, a white precipitate of barium sulphate is produced along with copper chloride solution.
CuSO₄ (aq) + BaCl₂ (aq) → BaSO₄ (s) + CuCl₂ (aq)

● It is an example of precipitation reaction.

● It is also a double displacement reaction since two compounds namely barium chloride and copper sulphate react by exchanging of their ions to form two new compounds, barium sulphate and copper chloride.

Chlorofluorocarbon (CFCs), commonly known by the DuPont brand name Freon, are considered as one of the ozone-depleting substances (ODS).

● Because CFCs contribute to ozone depletion in the upper atmosphere, the manufacture of such compounds has been phased out under the Montreal Protocol (1987).
They are being replaced with Hydrofluorocarbons (HFCs).

Carbon is a non-metal with atomic number 6. This means it has 6 protons and 6 electrons.

● The electronic configuration of carbon is 1s² 2s² 2p²

● To get the octet in its outer shell, it has to gain 4 more electrons to form C⁴⁻ ion.
However, it will have 10 electrons and 6 protons, making it very unstable.

An acidic solution turns blue litmus red.

● On the pH scale, acids have values less than 7, whereas bases have values greater than 7.

● Solutions with pH equal to 7 are neutral in nature.
Therefore, the pH of the given solution is likely to be 5.