Subject

Chemistry

Class

NEET Class 12

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 Multiple Choice QuestionsMultiple Choice Questions

1.

Which of the following, is not a unit of pressure?

  • Atmosphere

  • Torr

  • Pascal

  • Newton


D.

Newton

Newton is not the unit of pressure. It is the unit of force. Atmosphere, torr and pascal (Pa) are the units of pressure.

1 atm = 1.01 x 105 Pa

1 torr = 133.3 Pa


2.

A golf-ball weigh 40.0 gm. If it is moving with a velocity of 20.0 ms-1, it's de-Broglie wavelength is

  • 1.66 x 10-34 nm

  • 8.28 x 10-32 nm

  • 8.28 x 10-25 nm

  • 1.66 x 10-24 nm


C.

8.28 x 10-25 nm

From de-Broglie equation,

λ = hmv λ = 6.626 × 10-34 Js40 × 10-3 kg × 20.0 ms-1        = 8.28 × 10-34 m        = 8.28 × 10-34 × 109 nm        = 8.28 × 10-25 nm   


3.

The enthalpies of all elements in their standard states are

  • zero

  • >0

  • <0

  • unity


A.

zero

The enthalphy of elements are zero in their standard state.


4.

Volume of CO2 obtained from complete decomposition of 20 g CaCO3 at STP is

  • 2.24 litre

  • 4.48 litre

  • 20 litre

  • 22.4 litre


B.

4.48 litre

CaCO3(40 + 12 + 3 × 16)= 100 CaO + CO222.4 litre

 100 gm of CaCO3, on decomposition, gives 22.4 litre CO2 at STP

 20 gm of CaCO3, on decomposition, will give

 = 22.4 × 20100 = 4.48 litre CO2 at STP.


5.

Which of the following order of ionisation energy is correct?

  • B < Be < N < C

  • Be > B > C > N

  • B < Be < C < N

  • Be < B < C < N


C.

B < Be < C < N

Ionisation energy generally increase in a period from left to right. But due to comparatively stabler configuration of Be (1s2, 2s2), it has more ionisation energy than Boron (1s2, 2s2, 2p1) Hence, the correct order is : B < Be < C < N.


6.

Which of the following acids is monobasic?

  • H3PO3

  • H3PO2

  • H2SO3

  • H3PO4


B.

H3PO2

H3PO2 or hypophosphorus acid is a monobasic acid. It gives only one type of salt e.g., NaH2PO2.


7.

Which is the shortest wavelength line in the Lyman series of the hydrogen spectrum? (R= 1.097 x 10-2 nm-1)

  • 94.21 nm

  • 91.16 nm

  • 911.6 nm

  • 933.6 nm


B.

91.16 nm

For Lyman series, 1λ = R112 - 1n2

Hence, for λ to be smallest, n should be greatest (i.e. )

 1λmin = 1.097 × 10-2                = 1.097 × 10-2or λmin = 11.097 × 10-2 = 91.16 nm

91.16 nm is the shortest wavelength line in the Lyman series of the hydrogen spectrum.


8.

Which of the following ions, has smallest size?

  • Ca2+

  • Cl-

  • S2-

  • K+


A.

Ca2+

Ca2+, Cl-, S2- and K+ are isoelctronic species. In isoelectronic ions, size decrease with increasing nuclear charge. Hence, Ca2+ ion is the smallest among these.


9.

The significant figures in 1.0024, 1.240 and 0.0020 are respectively

  • 5, 4, 2

  • 3, 3, 1

  • 5, 3, 4

  • 5, 3, 2


A.

5, 4, 2

In 1.0024, all figures are significant.

In 1.240,the significant figures are four (zero tells about precision). Zero before a number are not significant, hence, 0.0020 has only two significant numbers (2 and 0 after 2).


10.

The shape of an orbital is determined by

  • n

  • l

  • m

  • s


B.

l

The azimuthal quantum number (l) determines the shape of an orbital. Fore.g.

l = 0 (spherical, s)

l = 1 ( dumb- bell, p) and so on.