Chemistry - Study Mode

[#796] Threshold limit value of copper in the atmospheric air is
Correct Answer

(C) 1.0 mg/m 3

Explanation

Solution: The threshold limit value (TLV) of copper in atmospheric air is 1.0 mg/m 3 .

[#797] Which one of the following minerals is found in Monazite sand ?
Correct Answer

(C) Thorium

Explanation

Solution: Monazite is an important ore for thorium, lanthanum, and cerium. It is often found in placer deposits. India, Madagascar, and South Africa have large deposits of monazite sands. The deposits in India are particularly rich in monazite.

[#798] Which of the following is the main compound of voter ink?
Correct Answer

(A) Silver nitrate

Explanation

Solution: The chemical used in voting inks is silver nitrate. Silver nitrate is preferred because it is soluble in water, and makes an inky black solution. When put on the skin, silver nitrate reacts with the salt present on it to form silver chloride that is insoluble in water, and clings to the skin, making it impossible to wash off with soap and water or even alcohol. Mysore Paints and Varnish Limited in Karnataka is only company in India authorised to produce the indelible ink.

[#799] The heaviest naturally occurring element is:
Correct Answer

(D) Uranium

Explanation

Solution: The heaviest naturally stable element is uranium, but over the years physicists have used accelerators to synthesize larger, heavier elements. In 2006, physicists in the United States and Russia created element 118.

[#800] In which of the following ions , the colour is not due to d-d transition ?
Correct Answer

(C) [CrO 4 ] 2āˆ’

Explanation

Solution: The colour of transition-metal compounds is normally associated with d-d transitions. However, some transition metal compounds show intense colour in solution in spite of absence of d-electrons. For example, the orange colour of TiBr 4 , yellow colour of CrO 4 2- , orange colour of Cr 2 O 2 7- , intense red colour of [Fe(SCN) 4 ] and deep purple of MnO 4 are not due to dā€”d transitions. In the case of MnO 4 ion, the color is due to charge transfer and not due to d-d transitions.