Practice MCQ Questions and answers on Chemistry-GK

Nitrogen is chemically unreactive because it has a strong triple bond which binds the two nitrogen atoms together making it harder for it to be broken. It does not burn, and at ordinary temperatures it does not react with other elements.

The red, orange, yellow, green, blue and purple colors exploding in the night sky during a pyrotechnic festival are created by the use of metal salts. Barium chloride provides green colour to firework displays. Metal salts that are commonly used in firework displays include: strontium carbonate (red), calcium chloride (orange), sodium nitrate (yellow), barium chloride (green fireworks) and copper chloride (blue fireworks).

Question: Deep-sea divers breathe a special mix of gases to stay safe underwater. Oxygen is part of the mix, but what other gas is commonly added?

Explanation: Divers need to breathe underwater, just like we do on land. Oxygen is essential for life, but breathing pure oxygen at high pressure (like deep underwater) can be dangerous.

That's why another gas is added to dilute the oxygen. Helium is the most common choice because it is:

1. Lightweight: This makes it easier to breathe at depth.

2. Inert: It doesn't react with the body or other gases.

3. Safe at high pressure: Unlike some other gases, helium doesn't cause problems when breathed under pressure at great depths.

Therefore, the correct answer is D: Helium.

A sodium-vapour lamp is a gas-discharge lamp that uses sodium in an excited state to produce light. There are two varieties of such lamps: low pressure and high pressure. Low-pressure sodium lamps are the most efficient electrical light sources, but their yellow light restricts applications to outdoor lighting such as street lamps. High-pressure sodium lamps have a broader spectrum of light but poorer colour rendering than other types. Because sodium vapour lamps cause less light pollution than mercury-vapour lamps, many cities that have large astronomical observatories employ them.

Zinc sulphate is not soluble in water.

Liquid Helium is the most volatile liquid.

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.

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.

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.

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.