SSC CGL GK Questions 2026

Temporary hardness is caused by the dissolved bicarbonates of calcium and magnesium. On boiling, these bicarbonates decompose into insoluble carbonates, which settle out as the scale seen in a kettle, so the water that remains is soft.

In a soda-acid extinguisher a solution of sodium hydrogen carbonate is kept in the body of the cylinder and sulphuric acid in a sealed glass phial.

When milk is set into curd, the bacteria Lactobacillus convert the milk sugar lactose into lactic acid, and it is this acid that gives curd its sour taste and makes the milk protein clot.

Aqua regia is a freshly prepared mixture of three parts concentrated hydrochloric acid to one part concentrated nitric acid. Neither acid alone attacks gold, but together they do, because the nitric acid oxidises the metal while the chloride ions hold the gold in solution as a complex.

Gypsum is calcium sulphate dihydrate, and heating it carefully to about 373 kelvin drives off three quarters of its water to leave calcium sulphate hemihydrate, which is Plaster of Paris.

It is a mild, non-corrosive base. In baking it releases carbon dioxide on heating and makes the dough rise, in medicine it neutralises excess acid in the stomach, and in a soda-acid fire extinguisher it reacts with sulphuric acid to produce the carbon dioxide that smothers the flame.

Boric acid dissolves in water to give a true solution, in which the dispersed particles are individual molecules small enough to pass through a filter paper and even a parchment membrane, and the mixture shows no Tyndall effect.

Rayon is made by dissolving the cellulose of wood pulp in a chemical and forcing the solution through fine holes to form filaments.

A dilute solution of iodine gives a deep blue-black colour with starch, which is a polysaccharide and therefore a carbohydrate.

In graphite each carbon atom is joined to only three other carbon atoms in flat hexagonal layers, so the fourth valence electron of every atom is not used in bonding and can move freely along the layer.

LHB stands for Linke Hofmann Busch, the German firm whose design Indian Railways adopted at the end of the 1990s and now builds at Kapurthala and other coach factories.

The Chenab bridge on that link stands about 359 metres above the bed of the river, higher than the Eiffel Tower, and is built as a steel arch to span the deep gorge in an earthquake prone and wind swept setting.

The correct answer is A, Gatimaan Express, which began running in 2016 between Delhi and Agra and became India's first semi-high-speed train at 160 kilometres an hour, a speed the Agra route could take because of its straight alignment and fenced sections.

The correct answer is B, the National High Speed Rail Corporation Limited, a company set up specifically to build and later operate high-speed rail in India, with the Union Government and the Governments of Gujarat and Maharashtra as shareholders.

The corridor uses the Shinkansen system, the high-speed technology Japan has run since 1964, and the project is financed largely by a soft loan from Japan carrying a long repayment period and a low rate of interest.

A Vande Bharat rake is a self-propelled electric multiple unit: the traction motors and control equipment are slung under the coaches themselves, so power is spread along the length of the train instead of being concentrated in one vehicle.

The first Vande Bharat Express was flagged off on 15 February 2019, after the train set had been built at the Integral Coach Factory under the name Train 18 and tested on Indian track.

The correct answer is B, the Integral Coach Factory at Chennai, which designed the train set under the project name Train 18 and rolled out the first rake.

Kavach works on the movement of trains: it reads the position and speed of a locomotive from trackside tags, compares that with the signal and the permitted speed, and brakes the train when the driver does not.

Safety Integrity Level is a scale of four grades used for safety related electronic systems, and level four is the most demanding, meaning the probability of a dangerous undetected failure is designed to be the lowest of all.