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NEET chemistry

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Question
CBSEENCH11008396
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Equal volumes of three acid solutions of pH 3.4 and 5 are mixed in a vessel. What will be the H+ ion concentration in the mixture?

  • 1.11 x 10-4 M

  • 3.7 x 10-4 M 

  • 3.7 x 10-3 M

  • 1.11 x 10-3 M

Solution

B.

3.7 x 10-4 M 

[H]+ in mixture
[H]+ of 1st acid x its volume + [H+]
of IInd acid  x its volume + [H+] of 

equals fraction numerator IIIrd space acid space straight x space its space volume over denominator Total space volume end fraction straight M space equals fraction numerator straight M subscript 1 straight V subscript 1 space plus straight M subscript 2 straight V subscript 2 space plus space straight M subscript 3 straight V subscript 3 over denominator straight V end fraction
Assume the volume of each solution is 1 L.
[H3O+] in solution of pH = 3 is 10-3M
[H3O+] in solution of pH = 4 is 10-4 M
[H3O+] in solution is pH is 5 is 10-5 M
Total space left square bracket straight H subscript 3 straight O to the power of plus right square bracket space equals space space fraction numerator 10 to the power of negative 3 end exponent space plus 10 to the power of negative 4 end exponent plus 10 to the power of negative 5 end exponent over denominator space 3 end fraction space equals space 0.00037 equals 3.7 space straight x space 10 to the power of negative 4 end exponent space straight M

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Question
CBSEENCH11008397
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The angular shape of ozone molecule (O3) consists of 

  • 1 sigma and 2 pi bonds

  • 2 sigma and 2 pi bonds

  • 1 sigma and 1 pi bonds

  • 2 sigma and 1 pi bonds

Solution

D.

2 sigma and 1 pi bonds

Single bond contains = 1 σ bond
Double bond contains = 1 σ bond + 1 π bond
Triple bond contains = 1σ  bond + 2 π bond
The molecule of O3 is bent with an angle of 116.8o and equal O-O distance of 128 pm. The ozone molecule consists of 2 sigma bond and 1 pi bond.

Question
CBSEENCH11008399
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Which of the following are not state functions?
I) q + W
II) q
III) W
IV) H-TS

  • (I) and (IV)

  • (II) (III) and (IV)

  • (I), (II) and (III)

  • (II) and (III)

Solution

D.

(II) and (III)

A state function is the property of the system whose value depends only on the initial and final state of the system and is independent of the path.
Therefore, 
Internal energy (ΔE) = q +W
It is a state function because it is independent of the path. It is an extensive property.
∴ Gibbs energy (G) = H -TS
It is also a state function because it is independent of the path. It is also extensive property. 
Heat (q) and work (W) are not state functions being path dependent.

Question
CBSEENCH11008400
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If uncertanity in position and momentum are equal, then uncertaninty in velocity is 

  • fraction numerator 1 over denominator 2 straight m end fraction square root of straight h over straight pi end root
  • square root of fraction numerator straight h over denominator 2 straight pi end fraction end root
  • 1 over straight m square root of h over pi end root
  • square root of straight h over straight pi end root

Solution

A.

fraction numerator 1 over denominator 2 straight m end fraction square root of straight h over straight pi end root

According to Heisenberg's uncertainty principle, it is impossible to determine simultaneously the position and momentum of moving a particle, ie.
left parenthesis increment straight x right parenthesis space straight x space left parenthesis increment straight p right parenthesis space greater or equal than fraction numerator straight h over denominator 4 straight pi end fraction Here comma space increment straight x space equals space increment straight p space equals space straight m. increment straight v increment straight v squared space equals space fraction numerator straight h over denominator straight m squared 4 straight pi end fraction increment straight v space equals space fraction numerator 1 over denominator 2 straight m end fraction square root of straight h over straight pi end root
The uncertainty principle in terms of energy and time is given as
increment straight E. increment straight t space greater or equal than space fraction numerator straight h over denominator 4 straight pi end fraction

Question
CBSEENCH11008401
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The correct order of decreasing second ionisation enthalpy of Ti (22), V (23), Cr(24) and Mn (25) is 

  • Cr > Mn> V > Ti

  • V > Mn > Cr >Ti

  • Mn > Cr> Ti >V

  • Ti >V >Cr> Mn

Solution

A.

Cr > Mn> V > Ti

The amount of energy required to remove an electron from unipositive ions is called the second IP which generally increases in a period from left to right.
The second ionisation energies of the first transition series increase almost regularly with an increase in atomic number. However, the value for Cr is sufficiently higher than those of its neighbour ie, (Mn). This is due to the stable configuration of Cr3+ (3d5 exactly half filled.)

[Note: The half-filled and completely filled configuration are more stable.]

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