Chemistry - Study Mode

[#321] Phosphorus is kept in water because
Correct Answer

(B) Its ignition temperature is very low

Explanation

Solution: White phosphorus is highly reactive, and spontaneously ignites at about 30°C in moist air. It is usually stored under water, to prevent exposure to the air. It is also extremely toxic, even in very small quantities.

[#322] The element which is used for vulcanizing rubber
Correct Answer

(A) Sulphur

Explanation

Solution: Vulcanization gives rubber its characteristic elastic quality. This process is carried out by mixing the latex with sulphur (other vulcanizing agents such as selenium and tellurium are occasionally used but sulphur is the most common) and heating it in one of two ways.

[#323] The weight of 6.023 × 10 23 atoms of carbon is
Correct Answer

(A) 12 gms

Explanation

Solution: The number 6.023 ×10 23 is known as Avogadro’s Number which is the number of atoms in 12g of the isotope carbon-12. 6.023 ×10 23 carbon atoms weigh = 12 grams.

[#324] If there is one million Mg 2+ ions in MgCl 2 , how many chloride ions are there?
Correct Answer

(A) Two million

Explanation

Solution: There are two million chloride ions.

[#325] What is the mass percentage of carbon in carbon dioxide (CO 2 )?
Correct Answer

(C) 27.3 %

Explanation

Solution: The mass percentage of carbon in carbon dioxide is 27.3 %.