Practice MCQ Questions and answers on Chemistry-GK

The atomic number of mercury is 80.

Bond order is a measure of the number of chemical bonds between two atoms in a molecule. It is calculated as (Number of bonding electrons - Number of anti-bonding electrons) / 2. For the molecule NO (nitric oxide): The number of bonding electrons is 5 (1 from N and 2 each from the 2 O atoms). The number of anti-bonding electrons is 2 (1 each from the 2 O atoms). The bond order is calculated as (5 - 2) / 2 = 3 / 2 = 1.5. Therefore, the correct answer is Option D: NO, and it has a bond order of 2.5.

Copper (Cu) has the atomic number of 29. Copper belongs to the d-block which is the collective name for Groups 3 to 12 in the periodic table. Most of the d-block elements are considered to be metals, with a common lustrous metallic appearance.

Osmium is the heaviest element of all (22.61g per cubic centimetre).

Aluminium forms one stable oxide, known by its mineral name corundum. Sapphire and ruby are impure corundum contaminated with trace amounts of other metals. Corundum is a crystalline form of aluminium oxide (Al₂O₃) with traces of iron, titanium and chromium. It is a rock-forming mineral. It is one of the naturally clear transparent materials, but can have different colours when impurities are present. Transparent specimens are used as gems, called ruby if red and padparadscha if pink-orange. All other colours are called sapphire, e.g., “green sapphire” for a green specimen. Because of corundum’s hardness (pure corundum is defined to have 9.0 Mohs), it can scratch almost every other mineral. It is commonly used as an abrasive, on everything from sandpaper to large machines used in machining metals, plastics, and wood. Some emery is a mix of corundum and other substances, and the mix is less abrasive, with an average hardness near 8.0.

Quartz is a compound of one part silicon and two parts of oxygen, silicon dioxide, SiO₂. Quartz is the most abundant silica mineral. It is used in a number of industries, the important being glass, foundry, sodium silicate, silicon alloys, etc. The various grades of sodium silicate are characterized by their SiO₂:Na₂O weight ratio.

Sodium chloride is the most common salt in sea water.

A growth fertilizer will have a high N content and relatively low P and K content. Ammonium nitrate is the highest Nitrogen fertilizer you can buy, and it is potent stuff. It is usually rated as 33-0-0 or 34-0-0. The bag contains 33% or 34% Nitrogen and the other 66% or 67% is inert material. Other formulations of growth fertilizers will contain 5, 6 or even 7 times more Nitrogen than anything else.

The most common type of kidney stone is a calcium oxalate stone. These result when the urine contains low levels of citrate and high levels of calcium and either oxalate or uric acid. Calcium oxalate stones are linked with foods high in oxalate, which is a naturally occurring substance in plants and animals.

Gypsum is added in calculated quantity in order to adjust the rate of setting of cement. Alum is not present in cement.