1099+ Important Chemistry MCQ Questions Answers

Q:

NH3 oxidation number?

A) -1	B) +1
C) 0	D) -3

Answer & Explanation Answer: C) 0

Explanation:

NH3, Ammonia is a neutral compound as the individual oxidation numbers elements that make up the compound NH3 are Nitrogen (N) and Hydrogen (H) sum to zero.

We do not speak of the oxidation number of a molecule. We can speak of the oxidation numbers of the individual elements that make up the compound.

Here the oxidation number of Nirogen is -3 and that of Hydrogen is +1.

Now, NH3 = 1(-3) + 3(+1) = -3 + 3 = 0.

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Q:

The absolute value of charge on electron was determined by

A) J.J.Thomson	B) R.A. Millikan
C) Rutherford	D) Chadwick

Answer & Explanation Answer: B) R.A. Millikan

Explanation:

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Q:

The discovery of neutron became very late because

A) it is present in nucleus	B) it is a fundamental particle
C) it does not move	D) it does not carry any charge

Answer & Explanation Answer: D) it does not carry any charge

Explanation:

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Q:

What is the IUPAC name of [Co(NH3)4Cl2]?

A) Tetra-ammine dichloro cobalt (III) chloride	B) Tetra-ammine trichloro cobalt (III)
C) Tri-ammine dichloro cobalt (III) chloride	D) Tetra-ammine dichloro cobalt

Answer & Explanation Answer: A) Tetra-ammine dichloro cobalt (III) chloride

Explanation:

The IUPAC nomenclature in organic chemistry is a systematic method that is used to name organic chemical compounds as recommended by the International Union of Pure and Applied Chemistry (IUPAC).

The IUPAC name of the given complex [Co (NH₃)₄Cl₂ ]Cl is - Tetra-ammine dichloro cobalt (III) chloride.

The complex [Co (NH₃)₄ Cl₂ ] Cl ionizes an aqueous solution to furnish the chloride ion Cl⁻ and [Co (NH₃)₄ Cl₂ ] ⁺.

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Q:

How many electrons are there in Na+

A) 1	B) 10
C) 11	D) 12

Answer & Explanation Answer: B) 10

Explanation:

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Q:

Temporary hardness is due to the presence of

A) Calcium carbonate	B) calcium bicarbonate
C) magnesium sulphate	D) calcium sulphate

Answer & Explanation Answer: B) calcium bicarbonate

Explanation:

Temporary hardness is due to the presence of soluble bicarbonates of calcium and magnesium in water. Permanent hardness is due to the presence of sulphates and chlorides of calcium and magnesium.

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Q:

The electrochemical cell stops working after some time because ________

A) Electrode potential of both the electrodes becomes zero	B) One of electrodes completely vanishes
C) Electrode potential of both electrodes equalizes	D) The reaction reverses its direction

Answer & Explanation Answer: C) Electrode potential of both electrodes equalizes

Explanation:

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Q:

The entropy change involved in the isothermal reversible expansion of 2 moles of an ideal gas from a volume of 10 $d m^{3}$ at 27°C is to a volume of 100 $d m^{3}$

A) 42.3 J/ mole / K	B) 38.3 J/ mole / K
C) 35.8 J/ mole / K	D) 32.3 J/ mole / K

Answer & Explanation Answer: B) 38.3 J/ mole / K

Explanation:

$∆ s = n R \ln \frac{v 2}{v 1}$

$= 2.303 n R \log \frac{v 2}{v 1}$ = $2.303 \times 2 \times 8.314 \times \log (\frac{100}{10})$ = $38.3 J$ $m o l^{- 1}$ $k^{- 1}$

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