Chemistry - Study Mode

[#896] The three elements most needed in common fertilisers are :
Correct Answer

(B) Nitrogen, Potassium and Phosphorous

Explanation

Solution: Fertilizer (or fertiliser) is any organic or inorganic material of natural or synthetic origin (other than liming materials) that is added to a soil to supply one or more plant nutrients essential to the growth of plants. The three elements most needed in common fertilisers are Nitrogen. Potassium and Phosphorous.

[#897] Liquid Nitrogen boils at
Correct Answer

(A) 77 kelvin

Explanation

Solution: Liquid nitrogen is very cold! At normal atmospheric pressure, nitrogen is a liquid between 63 K and 77.2 K (-346°F and -320.44°F). Over this temperature range, liquid nitrogen looks much like boiling water. Below 63 K, it freezes into solid nitrogen. Because liquid nitrogen in a usual setting is boiling, its usual temperature is 77 K.

[#898] Which one of the following is not a fertilizer?
Correct Answer

(B) Calcium sulphate

Explanation

Solution: Calcium sulfate is a common laboratory and industrial chemical. In the form of -anhydrite (the nearly anhydrous form), it is used as a desiccant. It is also used as a coagulant in products like tofu. The main sources of calcium sulfate are naturally occurring gypsum and anhydrite which occur at many locations worldwide as evaporites.

[#899] Which of the following gases is mixed with oxygen for breathing by divers in aqua lungs?
Correct Answer

(C) Helium

Explanation

Solution: Divers need to breathe underwater, right? But they can't just breathe regular air from the surface. The air we breathe is mostly nitrogen and oxygen. At great depths, nitrogen can have some bad effects on the body. That's why divers use a special mix of gases. This special mix often includes oxygen, of course, because we need oxygen to live. But instead of using all nitrogen, they mix in another gas that is safer at depth. Helium is a much safer choice because it doesn't cause the same problems as nitrogen at high pressures. So, the answer isn't methane, nitrogen, or hydrogen. The right answer is helium because it's used with oxygen in scuba tanks to allow divers to breathe safely at depth.

[#900] Which of the following is used as non-stick coating for cooking utensils?
Correct Answer

(D) Teflon

Explanation

Solution: The modern non-stick pans were made using a coating of Teflon (polytetrafluoroethylene or PTFE).