Subject

Chemistry

Class

NEET Class 12

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 Multiple Choice QuestionsMultiple Choice Questions

1.

For endothermic reaction :

  • Ea > Ea'

  • Ea = Ea'

  • Ea < Ea'

  • None of these


A.

Ea > Ea'

If the potential energy ofthe products is greater than that of the reactants , the energy released in going from the activated complex to products will be less than the activation energy and reaction willbe endothermic .

A + B Ea [AB]activated complex Ea'

Ea > Ea'


2.

When Al1327 is bombarded with α - particle , a radioactive isotope of phosphorus P1530 is formed .Which particle is emitted along with P1530 ?

  • Deuteron

  • Proton

  • Electron

  • Neutron


D.

Neutron

when Al1327 is bombarded with α - particle , then P1530 is formed along with n01 .

Al1327 + He42  P1530 + n01


3.

The product formed is an isobar , if there is :

  • α emission

  • β emission

  • α and 1 β emission

  • α and 2 β emission


B.

β emission

Xnm - β Xn + 1m

The atoms of different elements having different atomic number but same mass number are called isobars .So , by emission of one β particle isobar is obtained .


4.

Solution of 0.l N NH4OH and 0.1 N NH4Cl has pH 9.25. Then , pKb of NH4OH is :

  • 9.75

  • 4.75

  • 3.75

  • 8.25


B.

4.75

pOH = pKb + log[salt][base]

  [NH4Cl] = [NH4OH]

   pOH = pKb

pKb = pOH = 14 - pH

= 14 - 9.25 = 4.75


5.

How many grams of CO2 will be produced by the complete combustion of 2 moles of ethanol ?

  • 132 g

  • 44 g

  • 176 g

  • 88 g


C.

176 g

C2H5OH 1 mole = 46g + 3O2  2CO22 moles = 88 g + 3H2O

1 mole (46 g) C2H5OH gives = 88 g CO2

2 moles (92 g) C2H5OH will give = 176 g CO2


6.

The difference between heat of reaction at constant pressure and constant volume of the reaction :

2C6H6 (l) + 15O2 (g)  12CO2 + 6H2O (l)

at 25°C (in kJ) is :

  • - 7.43

  • 3.72

  • - 3.72

  • 7.43


A.

- 7.43

 H = E + ngRT

     H - E = ngRT

= - 3 x 8.314 x 10-3 x 298

= - 7.43kJ


7.

Heat of combustion of C and CO are -394 and -285 kJ respectively , so heat of formation of CO in kJ/mol is :

  • - 218

  • - 109

  • + 109

  • + 218


B.

- 109

C (s) + 12 O2 (g)  CO (g)

H = - [c H of CO - c H of C]

= - [-285-(-394)] kJ

= - 109 kJ


8.

Which of the following changes with change in temperature ?

  • Mole fraction

  • Formality

  • % (w/W)

  • Molality


B.

Formality

Formality is the-number of formula weights present in one litre of the solution .Formality changes withtemperature because it involves volume which change with temperature .


9.

The concentration of Ag+ ion in a given saturated solution of AgCl at 25°C is 1.06 x 10-5 g ion L-1 .Thus , the solubility product of AgCl is :

  • 0.453 x 10-10

  • 0.530 x 10-10

  • 1.12 x 10-10

  • 2.12 x 10-10


D.

2.12 x 10-10

AgCl  Ag+s + Cl-s

[Ag+] = [Cl-] = 1.06 x 10-5 g ion/L

Ksp = [Ag+] [Cl-] = S2

= (1.06 X l0-5)2 = 1.12 X 10-10


10.

For which reaction will H - E = 0 ? Assume that each reaction is carried out in an open container .

  • 2CO2 (g) + O2 (g)  2CO2 (g)

  • PCl5 (g)  PCl3 (g) + Cl2 (g)

  • H2 (g) + Br2 (g)  2HBr (g)

  • C (s) + 2H2O (g)  2H2 (g) + CO2 (g)


C.

H2 (g) + Br2 (g)  2HBr (g)

H = E + ngRT

For reaction H2 (g) + Br2 (g)  2HBr (g)

ng = 0 , while for other ng  0

Thus , H = E + 0 x RT

H - E = 0