SSC CGL GK Questions 2026

Bleaching powder, calcium oxychloride, is made in industry by passing chlorine gas over dry slaked lime, that is calcium hydroxide.

Tooth enamel is made of calcium phosphate, the hardest substance in the body, and it begins to corrode when the pH in the mouth drops below about 5.5.

A salt takes its character from the strength of the acid and the base that formed it. Ammonium chloride comes from hydrochloric acid, a strong acid, and ammonium hydroxide, a weak base, so the strong partner dominates and the solution has a pH below seven.

The stomach wall secretes hydrochloric acid, which makes the gastric juice strongly acidic, helps the enzyme pepsin digest proteins and kills many germs swallowed with food.

Plaster of Paris is calcium sulphate hemihydrate, made by heating gypsum, which is calcium sulphate dihydrate, to about 373 kelvin so that it loses three fourths of its water of crystallisation.

The sting of an ant and the hairs of the nettle plant inject formic acid, also called methanoic acid, which is why the skin burns; rubbing on a mild base such as baking soda or the leaf of the dock plant relieves it by neutralising the acid.

Baking soda is sodium hydrogen carbonate, a mild, non corrosive base used as an antacid, as an ingredient of baking powder along with a mild edible acid such as tartaric acid, and in soda acid fire extinguishers, where it releases carbon dioxide.

Borax, sodium tetraborate, is the salt of a strong base, sodium hydroxide, and a weak acid, boric acid, so its solution in water is basic.

The pH is the negative logarithm of the hydrogen ion concentration, so each rise of one unit means the concentration has fallen to one tenth.

Citrus fruits such as orange, lemon, lime and grapefruit owe their sharp sour taste to citric acid, which is the acid textbooks name for this family and the one examiners expect here.

Hydrofluorocarbons were adopted as substitutes for chlorofluorocarbons in refrigeration and air conditioning because they do not harm the ozone layer, but they turned out to be very powerful greenhouse gases, so the Kigali Amendment of 2016 brought them under the Montreal Protocol with a schedule for reducing their use.

The day marks the signing of the Montreal Protocol on Substances that Deplete the Ozone Layer in 1987 and is observed every year with a theme announced by the United Nations.

Marble is calcium carbonate, and sulphur dioxide in polluted air, along with the sulphuric acid of acid rain, reacts with it to form calcium sulphate, so the stone loses its shine, turns yellow and becomes pitted and flaky.

These gases come from burning coal and oil in thermal power stations, smelters and vehicles, are oxidised in the atmosphere and dissolve in water droplets to form sulphuric acid and nitric acid, which come down as acid rain.

The Montreal Protocol was adopted in 1987 under the Vienna Convention of 1985 and sets the timetable by which countries must stop producing and using chlorofluorocarbons, halons, carbon tetrachloride, methyl chloroform and methyl bromide.

The Dobson unit, named after the scientist who built the instrument for measuring atmospheric ozone, expresses how thick the ozone column would be if all of it were brought down to the surface at standard temperature and pressure; a hundred Dobson units correspond to a layer one millimetre thick.

About nine tenths of the atmosphere's ozone lies in the stratosphere, roughly fifteen to thirty five kilometres above the surface, where ultraviolet rays split oxygen molecules and the free atoms combine with other oxygen molecules to make ozone.

Nitric oxide and nitrogen dioxide, together written as nitrogen oxides, are air pollutants that come mainly from combustion in vehicles and power stations; they help form smog and acid rain but are not counted among the greenhouse gases of the natural atmosphere.

A primary pollutant is released directly from a source, while a secondary pollutant is formed in the atmosphere when primary pollutants react.

Each of the other three statements is correct on its own, which is exactly why the combined option is the answer.