General Science Questions (MCQs) for Competitive Examinations

Notes:
Radon was once commonly used to treat cancer. The radiation it gives off kills cancer cells. However, the element must be used with great care because radiation can kill healthy cells as well. In fact, the bad side-effects of radiation therapy are caused by the killing of healthy cells by radiation. Today, radon is not as widely used for the treatment of cancer.

Notes:
Transcription is the first step of gene expression, in which a particular segment of DNA is copied into RNA by the enzyme, RNA polymerase. During transcription, a DNA sequence is read by an RNA polymerase, which produces a complementary, antiparallel RNA strand. The transcribed direct and oversee the translation of genes into specific protein synthesis once in cytoplasm.

Notes:
The transport of soluble organic substances (sometimes called assimilates) within a plant is known as translocation. Both the symplast and the apoplast function in transport within tissues and organs of plants. Water passes into the stele through symplastic route and water passes into the xylem through apoplastic route.

Notes:
Valency of an element is a measure of its combining power with other atoms when it forms chemical compounds or molecules. It is the number of electrons present in outermost orbit of that element and refers to the tendency to attain octet configuration. Atoms would react to attain an octet configuration, that is, stable configuration, by gaining, losing or sharing electrons.

Notes:
The main gases responsible for causing acid rain are sulphur dioxide as well as nitrous oxides. The main sources of sulphur dioxide are metal working industries and coal-fired power stations whereas nitrous oxide is from vehicles and fuel combustion.

Notes:
The molar mass is the mass of a given chemical element or chemical compound (g) divided by the amount of substance (mol). The molar mass of the given noble gases are as follows:

• Argon (Ar): 39.9480 g/mol;
• Neon (Ne): 50.1858 g/mol;
• Krypton (Kr): 83.7980 g/mol;
• Xenon (Xe): 131.2930 g/mol.

Notes:
The atmosphere of the Earth is an envelope of gases extending to a height of 200km. It includes troposphere, slratosphere, inonosphere and thermosphere.

Notes:
Typical organic compounds are combustible by nature as they contain carbon. Organic compounds mostly consist of carbon, hydrogen, halogen, and phosphorus.

Notes:
Liquefied petroleum gas (LPG) is mostly propane (C3H8), mostly butane (C4H10) and, most commonly, mixes including both propane and butane. In the northern hemisphere winter, the mixes contain more propane, while in summer, they contain more butane.

Notes:
Ethanol is an alcohol-based fuel that is mostly produced by the fermentation of sugarcane juice and molasses. Because it is a clean, affordable and low-carbon biofuel, sugarcane ethanol has emerged as a leading renewable fuel for the transportation sector. The largest single use of ethanol is as an engine fuel and fuel additive.