Chemistry MCQs

Notes:
Among the given options, mercury has the lowest melting point of -38.83 °C. in fact, Mercury has the lowest melting point among all metals and is the only metal that exists as liquid at room temperature. The melting point of Carbon, Silver and Gold is 3550 °C, 961.78 °C and 1064.18 °C respectively.

Notes:
Aluminium is the most abundant metal in the earth’s crust. Aluminium does not occur free in nature, but its compounds are numerous and widely distributed. The chief and important ore from which aluminium is exclusively obtained is Bauxite. Corundum and Cryolite are also important ores of aluminium.

Notes:
Rose’s metal is an alloy of bronze, bismuth, lead and tin. It consists of 50% bismuth, 25–28% lead and 22–25% tin. It is a fusible alloy with a low melting point. It was discovered by the German chemist Valentin Rose the Elder, the grandfather of Heinrich Rose.

Notes:
In the history of the periodic table, Dobereiner’s triads were an early attempt to sort the elements into some logical order by their physical properties. He identified elements with similar properties and grouped them into groups of three, called “triads”. He also noted that some properties of elements in a triad followed a trend whereby the value of the middle element would be predicted by taking the arithmetic mean of values for that property of the other two elements.

Notes:
Nitrous oxide (NO), commonly known as laughing gas or happy gas, is the most commonly used inhalation anesthetic in dentistry and is commonly used in emergency centers and ambulatory surgery centers as well. It is an inorganic inhalation agent that is colorless, odorless to sweet-smelling, and non-irritating to the tissues.

Notes:
Photochemical smog is a unique type of air pollution which is caused by reactions between sunlight and pollutants like hydrocarbons and nitrogen dioxide (NO and NO2). Other components of the photo-chemical smog include Ozone (O3) formaldehyde, per-oxy benzoyl nitrate (PBzN), peroxy acetyl nitrate (PAN) and acrolein. The formation of photochemical smog can be expressed in the simple terms as:

• Hydrocarbons + NOX + sunlight.

Notes:
The pH level of lemon juice containing citric acid is, 5.00 to 5.60. It varies depending on the lemon. pH expresses different levels of acidity or alkalinity within a solution.

Notes:
There are three main natural sources of hydrocarbons: natural gas, petroleum and coal. Mica is a natural occurring mineral that is based on a collection of silicate minerals and composed of varying amounts of potassium, iron, aluminum, magnesium and water. It is widely used in the electrical industry.

Notes:
Ethylene (C2H4) is a nonpolar molecule. This is because, unlike a polar molecule, it has an even distribution of electrical charges. Since, the double bond is between two carbon atoms, there is no difference in the electronegativity. This is why, the shared pair of electrons come lie in between those to carbon atoms. As a result, ethylene is a non-polar and linear molecule.

Notes:
Pure water is a covalent compound. It exists as simple discrete molecules and has a simple molecular structure. Hence, it does not exist as ions. Therefore, pure water cannot conduct electricity due to the absence of mobile ions and electrons. How ever, water can conduct electricity in presence of some dissolved substance. Water then dissociate into hydrogen ions and hydroxide ions. The presence of these mobile ions enables it to conduct electricity.