Chemistry - Study Mode

[#706] Which of the following pairs of materials serves as electrodes in rechargeable batteries commonly used in devices such as torch lights, electric shavers, etc. ?
Correct Answer

(B) Nickel and cadmium

Explanation

Solution: A rechargeable battery, storage battery, or accumulator is a type of electrical battery. It comprises one or more electrochemical cells, and is a type of energy accumulator. It is known as a secondary cell because its electrochemical reactions are electrically reversible. Rechargeable batteries come in many different shapes and sizes, ranging from button cells to megawatt systems connected to stabilize an electrical distribution network. Several different combinations of chemicals are commonly used, including: lead–acid, nickel cadmium (NiCd), nickel metal hydride (NiMH), lithium ion (Li-ion), and lithium ion polymer (Li-ion polymer). Rechargeable batteries have lower total cost of use and environmental impact than disposable batteries. Some rechargeable battery types are available in the same sizes as disposable types. Rechargeable batteries have higher initial cost, but can be recharged very cheaply and used many times.

[#707] In a Carbonyl group a carbon atom makes double bond with
Correct Answer

(B) Oxygen

Explanation

Solution: In a Carbonyl group a carbon atom makes double bond with oxygen.

[#708] Williamson's synthesis is widely used in the laboratory preparation of
Correct Answer

(B) Ethers

Explanation

Solution: This is the most important industrial and laboratory method and may be used for preparing simple as well as mixed ethers.

[#709] German silver, an alloy, does not contain the metal
Correct Answer

(D) Silver

Explanation

Solution: German Silver is an alloy of copper, zinc, and nickel, sometimes also containing lead and tin. It does not contain silver metal and is extensively used because of its hardness and resistance to corrosion.

[#710] Removal of carbon particles from air involves the principle of
Correct Answer

(C) Electrophoresis

Explanation

Solution: Carbon particles in air are colloidal in nature and carry negative charge. The removal of carbon particles from air involves the principle of electrophoresis. Carbon particles get precipitated by losing their charge and, thus, the air which finally comes out is free from them.