Chemistry - Study Mode

[#106] Which of the following is colourless?
Correct Answer

(B) Oxygen

Explanation

Solution: Oxygen is colourless.

[#107] Iodine value is used to estimate
Correct Answer

(C) Unsaturation in oil

Explanation

Solution: Iodine value can be used to measure the degree of unsaturation of oils and fats. The results are normally expressed as the number of grams of iodine absorbed by 100 g of oil or fat, considering the conditions of the test.

[#108] The inert gas which is substituted for nitrogen in the air used by deep sea divers for breathing, is
Correct Answer

(D) Helium

Explanation

Solution: Helium (He) is an inert gas that is less narcotic than nitrogen at equivalent pressure (in fact there is no evidence for any narcosis from helium at all), so it is more suitable for deeper dives than nitrogen. Helium is equally able to cause decompression sickness.

[#109] A potato tuber has been cut into two halves. A few drops of iodine solution are placed on the cut surface of one of the halves. What colour change will be noticed?
Correct Answer

(A) From brown to blue-black

Explanation

Solution: The Iodine test is used to test for the presence of starch. Iodine solution — iodine dissolved in an aqueous solution of potassium iodide — reacts with the starch producing a purple black colour.

[#110] An electrochemical cell which is used as a source of direct electrical current at constant voltage under standard conditions is called a :
Correct Answer

(B) Battery

Explanation

Solution: A Galvanic cell, also known as battery, is an electrochemical cell that derives electrical energy from spontaneous redox reactions taking place within the cell. It is typically used as a source of electrical power. By their nature, they produce direct current. A battery is a set of galvanic cells that are connected in parallel.