Subject

Chemistry

Class

NEET Class 12

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 Multiple Choice QuestionsMultiple Choice Questions

11.

The density of SO2 at STP is 2.86 kg m3. Its density at 819°C and 2 atmospheres is:

  • 0.715 kg m-3

  • 1.43 kg m-3

  • 2.86 kg m-3

  • 4.26 kg m-3


B.

1.43 kg m-3

We have d = PMRT

or d1T1P1 = d2T2P2

According to the equation,

d1 = 2.86 kg m-3 , d2 = ?

T1 = 273K

T2 = 819 + 273 = 1092 K

P1 = 1 atm

P2 = 2 atm

 2.86 × 2731 = d2 × 10922

or d22 × 2.86 × 2731092

        = 1.43 kg m-3


12.

The molarity of pure water is:

  • 100

  • 55.6

  • 18

  • 5.56


B.

55.6

Molar mass of water = 18 g/mol

      Density of water = 1 g/mol

 1 l = 1000mL

 1l of water = 1000 gm

Molecules = massmolar mass = 1000 g18 g/mol

             = 55.56 mol water

Molarity = 55.56 mol1 L = 55.56 M


13.

When H2S gas is passed in a metal sulphate solution in presence of NH4OH, a white precipitate is produced. The metal is identified as

  • Zn

  • Fe

  • Pb

  • Hg


A.

Zn

Zinc is that metal, which gives white precipitate when H2S gas is passed in the ammonical solution of its salt.


14.

The most reactive hydrocarbon is :

  • methane

  • ethane

  • ethylene

  • acetylene


C.

ethylene

In ethylene H2C = CH2, the C - C bond distance is 1.34 Å, therefore, the π electrons of the double bond are easily exposed to the reactant (electrophiles) which readily react. In acetylene molecule HC  CH, although there are two π bonds but these electrons are not exposed to the attacking reagents due to small bond distance of C C bond (1.20 Å). A catalyst mercuric ion is therefore needed in reactions with actylene.


15.

Which of the following electronic configuration represents noble gas?

  • ns2np6

  • ns2np5

  • ns2np4

  • ns2np3


A.

ns2np6

Noble gases have fully filled valence shell electronic configuration. Therefore, it represents ns2np6 electronic configuration.


16.

H3PO3 is

  • dibasic acid

  • basic

  • tribasic acid

  • neutral


A.

dibasic acid

The P-H bond in H3PO3 is not ionisable and do not play any role in its basicity. Only those atoms which are attached to O in P-OH form are ionisable and are responsible for the basicity. Thus, H3PO3 is dibasic as it has two P-OH bond.


17.

35.4 mL of HCl is required for the neutralization of a solution containing 0.275 g of sodium hydroxide. The normality of hydrochloric acid is?

  • 0.97 N

  • 0.142 N

  • 0.194 N

  • 0.244 N


C.

0.194 N

We know that 1 gm equivalent weight of NaOH = 40 gm

 40 gm of NaOH = 1 gm equivalent of NaOH

 0.275 gm of NaOH = 140 × 0.275 eq.

                                = 140 × 0.275 × 1000

                                = 6.88 meq

                    N1V1 = N2V2

                N1 × 35.4 = 6.88 (  meq = NV)

                           N1 = 0.194

Therefore, 0.194 N is the normality of HCl. 


18.

The value of amu is which of the following?

  • 1.57 × 10-24 kg

  • 1.66 × 10-24 kg

  • 1.99 × 10-23 kg

  • 1.66 × 10-27 kg


D.

1.66 × 10-27 kg

amu represents atomic mass unit. It is used in place of unified mass unit.

1 amu = 1 Avogram = 1 Aston = 1 Dalton

1 amu = 112 ×  mass of C-12 atom

          = 112 × 1.9924 × 10-23 g

          = 1.66 × 10-24

          = 1.66 × 10-27 g

Therefore, the correct option is d.


19.

Lowest MP and BP is of

  • Ar

  • Xe

  • He

  • Ne


C.

He

The melting and boiling point of noble gases are low because of the presence of weak Van der Waals forces or weak London dispersion forces between the atoms of the noble gases.


20.

The molecule having largest dipole moment among the following is

  • CHI3

  • CH4

  • CHCl3

  • CCl4


C.

CHCl3

The molecule having largest dipole moment is CHCl3