General Science GK Questions with Answers – Page 102

All three are mixtures: wood is made of cellulose, lignin, water and resins, air is a mixture of nitrogen, oxygen and other gases, and sand is mostly silica mixed with mineral and shell grains.

Quick lime is calcium oxide, CaO, and not calcium carbonate, so it is the odd one out. Limestone, chalk and marble are all natural forms of calcium carbonate, CaCO3, differing only in how they were formed and in how hard they are.

Distilled water has had its dissolved salts removed, so it holds almost no free ions to carry charge and does not conduct electricity.

Time period is the time taken for one full oscillation, so it is the total time divided by the number of oscillations: 64 divided by 40 gives 1.6 seconds.

The LPG supplied in household cylinders is mainly a mixture of butane and propane, two gases that turn liquid under moderate pressure.

Only at -40 do the two scales read alike, so -40 °C and -40 °F are the very same temperature.

Concentration tells how much solute is present in a given amount of solution, and the three standard percentage forms are mass by mass, mass by volume and volume by volume; volume by mass is not one of them.

The Tyndall effect is the scattering of a beam of light by particles suspended in a medium, and it needs particles large enough to scatter that light.

Sulfur dioxide is made of one sulfur atom and two oxygen atoms, so its molecular mass is the sum of their atomic masses: 32 plus 2 multiplied by 16, that is 32 plus 32, which gives 64 u. Molecular mass is expressed in unified atomic mass units, written u, and…

Calcium chloride is an ionic compound, so it has a formula unit mass rather than a molecular mass, and the value is found by adding the atomic masses of all the atoms in the formula.

Bacteria in the mouth break down leftover food particles and produce acid, not base, so statement d is the incorrect one.

Litmus is a natural indicator obtained from lichens, which are a partnership between an alga and a fungus, and in a neutral solution it shows a purple colour.

A haloalkane carries a halogen atom - fluorine, chlorine, bromine or iodine - bonded to a carbon chain, so no oxygen appears in its functional group at all.

Cyclohexane is a closed ring of six carbon atoms joined by single bonds, and each carbon carries two hydrogen atoms, which gives C6H12.

The alkene series begins at two carbon atoms, so its first member is ethene, C2H4, and its second member is propene, C3H6.

C3H4 is propyne, and it fits the alkyne general formula CnH2n-2 when n equals 3. Alkynes are unsaturated hydrocarbons that carry at least one carbon-to-carbon triple bond, and the first member of the family is ethyne, C2H2, better known as acetylene and burnt with oxygen in welding torches.

Put n equal to 3 in the alkyne general formula CnH2n-2 and the result is C3H4, which is propyne, the second member of the alkyne series.

An alkene is an unsaturated hydrocarbon in which two carbon atoms are joined by a double bond, so the carbon-to-carbon double bond is its identity.

Alkanes are saturated hydrocarbons, so every bond between two carbon atoms is a single bond and all the remaining valencies are filled by hydrogen.

The d-block sits in the middle of the periodic table, bridging the s-block on the left and the p-block on the right.