1099+ Important Chemistry MCQ Questions Answers

Q:

Triple point of water corresponds to

A) 1 atm, 0°C	B) 1 atm, 0.01°C
C) 1 atm, 0 K	D) 4.58 Torr, 0.01°C

Answer & Explanation Answer: D) 4.58 Torr, 0.01°C

Explanation:

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Q:

Which reaction occurs spontaneously?

A) Cl2(g) + 2NaF(aq)--> F2(g) + 2NaCl(aq)	B) I2(s) + 2NaF(aq)--> F2(g) + 2NaI(aq)
C) Cl2(g) + 2NaBr(aq)-->Br2(l) + 2NaCl(aq)	D) I2(s) + 2NaBr(aq)--> Br2(l) + 2NaI(aq)

Answer & Explanation Answer: C) Cl2(g) + 2NaBr(aq)-->Br2(l) + 2NaCl(aq)

Explanation:

In this chemical reaction chlorine change oxidation number from 0 to -1 (reduction) and bromine change oxidation number from -1 to 0 (oxidation).

Chlorine is stronger oxidation reagent than bromine.

In VIIA or group 17 (halogen elements) there are six elements: fluorine (F), chlorine (Cl), bromine (Br), iodine (I), astatine (At) and tennessin(Ts).

They have high electronegativity because they have seven valence electrons in their outermost energy level, so they can gain an electron to have the octet rule.

Going down in the group, element are weaker oxidazing reagent and less reactive.

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Q:

Which one of the following orders presents the correct sequence of the increasing basic nature of the given oxides?

(1) $K_{2} O < N a_{2} O < A l_{2} O_{3} < M g O$

(2) $A l_{2} O_{3} < M g O < N a_{2} O < K_{2} O$

(3) $M g O < K_{2} O < A l_{2} O_{3} < N a_{2} O$

(4) $N a_{2} O < K_{2} O < M g O < A l_{2} O_{3}$

A) Option 1	B) Option 2
C) Option 3	D) Option 4

Answer & Explanation Answer: B) Option 2

Explanation:

While moving from left to right in periodic table basic character of oxide of elements will decrease.

$∴ \to_{I n c r e a \sin g b a s i c s t r e n g t h}^{A l_{2} O_{3} < M g O < N a_{2} O}$

and while descending in the group basic character of corresponding oxides increases.

$∴ \to_{I n c r e a \sin g b a s i c s t r e n g t h}^{N a_{2} O < K_{2} O}$

$∴ C o r r e c t O r d e r i s A l_{2} O_{3} < M g O < N a_{2} O < K_{2} O$

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Q:

Which one of the following can be oxidised to the corresponding carbonyl compound:

A) 2-methyl-2-hydroxy propane	B) 2-hydroxy propane
C) o-Nitrophenol	D) Phenol

Answer & Explanation Answer: B) 2-hydroxy propane

Explanation:

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Q:

Chloroform used as anaesthetic should be preserved in the dark in tightly stoppered bottles because otherwise

A) it becomes coloured	B) it gets evaporated in air
C) it gets oxidised to phosgene	D) it gets decomposed to chloropicrin

Answer & Explanation Answer: C) it gets oxidised to phosgene

Explanation:

Chloroform, $C H C l_{3}$ is easily oxidised to the highly poisonous gas known as phosgene or carbonyl chloride COCl2. Hence if it is used as anaesthetic it should be kept free from sunlight and air.

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Q:

Which of the following is the lightest metal?

A) Lithium	B) Silver
C) Mercury	D) Lead

Answer & Explanation Answer: A) Lithium

Explanation:

Lithium is the lightest of all the metals due to its low atomic number among metals. It is the lightest solid element.

Which_of_the_following_is_the_lightest_metal1552386560.jpg image

Properties ::

* It is a soft silvery-white alkali metal.

* Lithium is highly reactive and flammable and is stored in mineral oil.

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0 4657

Q:

Of the following radiations, the most easily stopped by air

A) alpha - rays	B) beta - rays
C) gamma -rays	D) x - rays

Answer & Explanation Answer: A) alpha - rays

Explanation:

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2 4638

Q:

Which one of the following laws directly expalins the law of coservation of mass

A) Hund's rule	B) Dalton's law
C) Avogadro's law	D) Berzelius hypothesis

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