Chemistry MCQs

Notes:
Lead is a naturally occurring bluish-gray metal found in small amounts in the earth’s crust. In the past, when lead was added to gasoline, breathing automobile exhaust was the major source of lead exposure and poisoning for most people. Lead in the exhaust also contaminated the soil near roads.

Notes:
Sodium bicarbonate and organic acid (Formic acid, Acetic acid, Carbonic acid, etc) react vigorously to liberate carbon dioxide. For example, Sodium bicarbonate (NaHCO3) when treated with acetic acid reacts vigorously to liberate carbon dioxide.

• NaHCO3 + CH3COOH —> CH3COONa + H2O + CO2

Notes:
Maximum permissible concentration of total hardness in drinking water in 200. It is a good source of minerals necessary for human health.

Notes:
As per the question, the half life of radioactive substance is 6 months. This means that half of the substance will disintegrate in 6 months. After the decay of the substance, only 50% of it remains. The half of the remaining substance (¼ th of the original substance) will then decay in another 6 months. So, three fourth or 75% of the substance will decay in 12 months of time.

Notes:
The Sun is a huge, glowing sphere of hot gas. Most of this gas is hydrogen (about 70%) and helium (about 28%). Carbon, nitrogen and oxygen make up 1.5% and the other 0.5% is made up of small amounts of many other elements such as neon, iron, silicon, magnesium and sulphur.

Notes:
Ethylene glycol (IUPAC name: ethane-1,2-diol) is an organic compound widely used as an automotive antifreeze and a precursor to polymers. In its pure form, it is an odorless, colourless, syrupy, sweet-tasting liquid. Due to its low freezing point ethylene glycol resists freezing. A mixture of 60% ethylene glycol and 40% water freezes at -45 degree C (-49 degree F).

Notes:
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.

Notes:
Linseed oil and castor oils are used mainly as drying agents in paints and varnishes. Linseed oil is generally used in the manufacture of oil paints, drying oil finish or varnish in wood finishing, as a pigment binder in oil paints, as a plasticizer and in the manufacture of linoleum.

Notes:
Graphite is a form of crystalline carbon in which each carbon atom is covalently bonded to three other carbon atoms.

• Diamond is a form of carbon in which each carbon atom is covalently bonded to four other carbon atoms.
• A fullerene (buckerminster-fullerenes) is a form of carbon in which carbon atoms are arranged in a hollow sphere resembling a soccer ball. Each sphere contains 60 carbon atoms, and each carbon atom is bonded to three others by single covalent bonds.
• Methane is the simplest hydrocarbon, consisting of one carbon atom and four hydrogen atoms.
• Methane is a powerful greenhouse gas.
• It is a principal component of natural gas.

Notes:
Melting points and boiling points of some compounds of carbon :
(Compound) – (Melting point)(K) – (Boiling point)(K)

• Acetic acid – (CH3 COOH): 290, 391
• Chloroform – (CHCl3): 209, 334
• Ethanol – (CH3CH2OH): 156, 351
• Methane – (CH4): 90, 111