Chemistry Questions

Q:

Under which conditions are gases most soluble in water?

A) low pressure and low temperature B) low pressure and high temperature
C) high pressure and low temperature D) high pressure and high temperature
 
Answer & Explanation Answer: C) high pressure and low temperature

Explanation:

Henry's Law tells that the solubility of a gas is directly proportional to the partial pressure of the gas above the solvent. Hence under high pressure, more gas is dissolved.

Also that Henry's Law involves a constant which is temperature-dependent. Under high temperatures, less gas is dissolved whereas under low temperatures, more gas is dissolved.

 

For Example ::  

You can think of a can of soda. The contents are under pressure and if you shake the can before opening, the soda fizzes out all over as you open it. So the higher the pressure, the more gas or more CO2 can be dissolved in the drink.

Eliminate choices 1 and 2. Now focus on the temperature. Soda goes flat (loses carbonation or gas) as it warms up. Soda is usually served cold because more of the carbonation or CO2 stays in the drink when the soda is cold.

 

Hence, in high pressure and low temperature conditions gases are most soluble in water.

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Q:

'Minamata' disease was caused by ?

A) Lead B) Mercury
C) Cadmium D) Zinc
 
Answer & Explanation Answer: B) Mercury

Explanation:
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Q:

Ozonolysis of an organic compound gives formaldehyde as one of the products. This confirms the presence of :

A) An acetylenic triple bond B) Two ethylenic double bonds
C) A vinyl group D) An isopropyl group
 
Answer & Explanation Answer: C) A vinyl group

Explanation:

C=}CH2OzonolysisHCHO

Vinylic group.

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Q:

One method by which the components of air can be seperated is 

A) shaking with caustic soda solution B) shaking with water
C) fractional distillation of liquid air D) passing air over heated magnesium
 
Answer & Explanation Answer: C) fractional distillation of liquid air

Explanation:

The two main components of air are nitrogen and oxygen. They are seperated by the fractional distillation of liquid air. Liquefied air contains liquid nitrogen and liquid oxygen. Liquid nitrogen with the lower boiling point more readily evaporates than the less volatile liquid oxygen. 

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Q:

A bond formed by sharing of electrons between atoms of the element is called

A) ionic bond B) covalent bond
C) co ordinate bond D) none
 
Answer & Explanation Answer: B) covalent bond

Explanation:
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Q:

The most abundant metal in earth crust is

A) Iron B) magnesium
C) calcium D) aluminium
 
Answer & Explanation Answer: D) aluminium

Explanation:
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Q:

Which sample is a pure substance?

A) Table salt B) Pure water
C) a test tube of zinc oxide D) All the above
 
Answer & Explanation Answer: D) All the above

Explanation:

A pure substance can be defined as any single type of material that has not been contaminated by another substance. In chemistry, a pure substance has a definite composition. It can be a compound or an element. A pure substance is considered to be a material that consists of one type of "building block" of matter.

Examples of pure substances include tin, sulfur, diamond, water, pure sugar (sucrose), table salt (sodium chloride) and baking soda (sodium bicarbonate).

Tin, sulfur, and diamond are examples of pure substances which are chemical elements. All elements are pure substances.

Water, sugar, salt and baking soda are pure substances which are chemical compounds. Chemical compounds also are pure substances

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Q:

Leakage in LP gas cylinders is easily detected by adding

A) mercaptans B) propylene
C) carbon disulphide D) phosgene
 
Answer & Explanation Answer: A) mercaptans

Explanation:

mercaptans (or thioalcohols) have a foul odour

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