Subject

Chemistry

Class

NEET Class 12

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 Multiple Choice QuestionsMultiple Choice Questions

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1.

Dimethyl glyoxime gives a red precipitate with Ni2+, which is used for its detection. To get this precipitate readily the best pH range is

  • < 1

  • 2-3

  • 3- 4

  • 9- 11


D.

9- 11

Nickel(II) forms a precipitate with the organic compound dimethylglyoxime, C4H6(NOH)2. The formation of the red chelate occurs quantitatively in a solution in which the pH is buffered in the range of 5 to 9. The chelation reaction that occurs is illustrated below.

The reaction is performed in a solution buffered by either an ammonia or citrate buffer to prevent the pH of the solution from falling below 5. If the pH does become too low the equilibrium of the above reaction favors the formation of nickel(II) ion, causing the dissolution of Ni(DMG)2 back into the mother liquor.


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2.

The statement true for N3- is

  • it has a non-linear structure

  • it is called pseudohalogen

  • the formal oxidation state of nitrogen in this anion is -1

  • it is isoelectronic with NO2


3.

Shape of O2F2 is similar to that of

  • C2F2

  • H2O2

  • H2F2

  • C2H2


4.

The liquefied metal expanding on solidification is

  • Ga

  • Al

  • Zn

  • Cu.


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5.

The compound insoluble in water is

  • mercurous nitrate

  • mercuric nitrate

  • mercurous chloride

  • mercurous perchlorate.


6.

The ONO angle is maximum in

  • NO3-

  • NO2-

  • NO2

  • NO2+


7.

The dipole moment is the highest for

  • trans-2-butene

  • 1,3-dimethylbenzene

  • acetophenone

  • ethanol.


8.

For principle quantum number n = 4, the total number of orbitals having l= 3 is

  • 3

  • 7

  • 5

  • 9


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9.

How much energy is released when 6 moles of octane is burnt in air? Given Hf° for CO2(g) , H2O(g) and C8H18(l)  respectively are - 490, -240 and +160 kJ/mol.

  • -6.2 kJ

  • -37.4 kJ

  • -35.5 kJ

  • -20.0 kJ


10.

For the equilibrium H2O(l)  H2O(g) at 1 atm and 298K.

  • standard free energy change is equal to zero (G°= 0)

  • free energy change is less than zero (G° < 0)

  • standard free energy change is less than zero (G°< 0)

  • standard free energy change is greater than zero (G° > 0).


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