Practice MCQ Questions and answers on Chemistry-GK

Helium is used to dilute the oxygen and nitrogen to reduce these affects. Helium is the gas of choice to use because it is an inert gas, is thinner, therefore more compressible than air, and its narcotic properties are negligible in comparison to nitrogen.

The only liquid elements at standard temperature and pressure are bromine (Br) and mercury (Hg).

Oxygen is found in maximum percentage in the human body.

Iodine is well known to sublime (change from solid to gas without becoming liquid inbetween) when heated. However sodium chloride has a melting point much higher than that of iodine. Therefore, a mixture of iodine and sodium chloride can be separated by using a sublimation apparatus, with solid iodine collected by condensation on a cold surface.

Trimix is a breathing gas, consisting of oxygen, helium and nitrogen, and is often used in deep commercial diving. The helium is included as a substitute for some of the nitrogen, to reduce the narcotic effect of the breathing gas at depth. It helps to reduce nitrogen narcosis and to avoid the dangers of oxygen toxicity. With a mixture of three gases, it is possible to create mixes suitable for different depths or purposes by adjusting the proportions of each gas.

Graphite is not a mixture. This is because graphite is a pure element which cannot split into its constituent particles.

Trimix is a breathing gas, consisting of oxygen, helium and nitrogen, and is often used in deep commercial diving. The helium is included as a substitute for some of the nitrogen, to reduce the narcotic effect of the breathing gas at depth. It helps to reduce nitrogen narcosis and to avoid the dangers of oxygen toxicity. With a mixture of three gases, it is possible to create mixes suitable for different depths or purposes by adjusting the proportions of each gas.

The most abundant element in the human body is oxygen.

Nitrogen is a fairly inert gas at room temperature and is the most abundant element in Earth's atmosphere.

Water (H₂O) is the most abundant compound on Earth's surface. Water is a compound because it contains oxygen and hydrogen which are chemically combined in proportion.