Chemistry - Study Mode

[#631] What material is used to make electric heater coil ?
Correct Answer

(D) Nichrome

Explanation

Solution: Nichrome is a non-magnetic alloy of nickel, chromium, and often iron, usually used as a resistance wire. Patented in 1905, it is the oldest documented form of resistance heating alloy. A common alloy is 80% nickel and 20% chromium, by mass, but there are many others to accommodate various applications. It is silvery-grey in colour, is corrosion-resistant, and has a high melting point of about 1400 degree C (2552 degree F). Due to its relatively high electrical resistivity and resistance to oxidation at high temperatures, it is widely used in electric heating elements, such as in hair dryers, electric ovens, soldering iron, toasters, and even electronic cigarettes. Typically, Nichrome is wound in coils to a certain electrical resistance, and current is passed through to produce heat.

[#632] Among the following, which is always found in free-state in nature?
Correct Answer

(A) Gold

Explanation

Solution: Gold is always found in free-state in nature.

[#633] Philosopher’s Wool is
Correct Answer

(C) Zinc oxide

Explanation

Solution: Philosopher’s Wool is Zinc oxide.

[#634] Which of the following metals has least melting point ?
Correct Answer

(C) Mercury

Explanation

Solution: Mercury has least melting point.

[#635] The main buffer system of the human blood is
Correct Answer

(A) H 2 CO 3 - HCO 3

Explanation

Solution: Bicarbonate buffer is the most important buffer system in blood plasma (generally in the extracellular fluid). This buffer consists of weak acid H 2 CO 3 (pK1 = 6,1) and conjugated base HCO 3 - (bicarbonate).