Practice MCQ Questions and answers on Chemistry-GK

Activated charcoal is used to remove colouring matter from pure substances. It works by adsorption. Colour impurities are adsorbed on the surface of activated charcoal.

The molecular mass of a gas is twice its vapour pressure.

The universal gas constant R signifies the work done by or on a gas per mole per kelvin. The SI unit of R is J mole^-1 K^-1 and its value is 8.314 J mole^-1 K^-1. In CGS unit, the value of R is 1.98 cal mol^-1 °C^-1.

The absolute temperature of a gas is doubled and the pressure is reduced to half, the volume of the gas will increase four-fold.

Isobars are imaginary lines joining the places having equal values of pressure. Closely spaced isobars indicate strong pressure gradient and widely spaced isobars indicate weak pressure gradient.

Two moles of an ideal gas expands spontaneously into vacuum, the work done is zero.

Yeasts are the main fermentor and alcohol producer in the production of wine, beer and other alcohol drinks. The main yeast species used is Saccharomyces cerevisiae. It ferments the sugars, coming from different sources, e.g., grapes for wine, barley for beer, to alcohol and carbon dioxide.

Denatured alcohol is ethanol that has additives to make it undrinkable (poisonous), to discourage recreational consumption. Different additives are used to make it difficult to use distillation or other simple processes to reverse the denaturation. Methanol is commonly used both because its boiling point is close to that of ethanol and because it is toxic.

A rectified alcohol is highly concentrated ethanol which has been purified by means of repeated distillation, a process that is called rectification. It typically contains 95% alcohol by volume and 5 % water. Normally, ethanol with 5 % water is known as pure alcohol.

Alcohol prepared by the distillation of wood is Methyl alcohol. It is also called wood spirit.