1099+ Important Chemistry MCQ Questions Answers

Q:

Which solution is most concentrated?

A) 6 g of solute in 10 ml of solution	B) 20.5 g of solute in 50 ml of solution
C) 30 g of solute in 120 ml of solution	D) 2.6 g of solute in 2 ml of solution

Answer & Explanation Answer: D) 2.6 g of solute in 2 ml of solution

Explanation:

A concentrated solution will contain the most solute molecules per solvent molecules.

Here in the given options,

1) 6/10 = 0.6

2) 20.5/50 = 0.41

3) 30/120 = 0.25

4) 2.6/2 = 1.3

Hence, option D) is most concentrated.

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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:

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:

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:

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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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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