Subject

Chemistry

Class

NEET Class 12

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 Multiple Choice QuestionsMultiple Choice Questions

31.

In the complex [Co(en)2Cl2 ] Br, the co-ordination number and oxidation state of cobalt are

  • 6 and +1

  • 6 and +3

  • 3 and +3

  • 4 and +2


B.

6 and +3

Ethylene diamine (en) is a bidentate ligand, i.e., it has two donor centres. In the complex [CO(en)2 Cl2 ]Br, the total number of donor atoms is 6 (4 from two 'en' moles + 2 Cl- ions).

Let the oxidation state of 'Co' be x.

+ (0 × 2) + (-1 × 2) + (-1) = 0

                          x + 0 - 2 - 1 = 0

                                     x - 3 = 0

                                          x = +3


32.

Rusting of iron is a chemical reaction. The reaction is :

  • double decomposition

  • combination

  • displacement

  • analysis


B.

combination

Rusting of iron is a type of redox reaction, i.e. a combination of both oxidation and reduction reaction. Hence, a combination reaction.


33.

Which of the following is coinage metal?

  • Cu

  • Sn

  • Zn

  • Pb


A.

Cu

Among all the given options, Cu is the coinage metal. 

A Group 11 element is one in the series of elements in group 11 in the periodic table, consisting of transition metals which are the traditional coinage metals of copper (Cu), silver (Ag), and gold (Au).


34.

Which one of the following colloidal solution is positive sol?

  • Gelatin in strongly acidic solution

  • Smoke

  • Dlay soil

  • Blood


A.

Gelatin in strongly acidic solution

Colloidal particles always carry an electric charge. It is of two types: Positive or Negative.

Positively charged sols consists of metallic hydroxide sols, dye stuffs, Haemoglobin etc.

Among all the given options, gelatin in strong acidic medium is the correct answer.


35.

Gasoline is

  • C17H36 to C21H50

  • C7H24 to C14H34

  • C7H16 to C10H22

  • C3H8 to C6H14


C.

C7H16 to C10H22

Gasoline is a petroleum-derived product comprising a mixture of liquid aliphatic and aromatic hydrocarbons, ranging between C4 and C12 carbon atoms with the boiling range of 30–225°C. 

Therefore, option c is correct.


36.

Percentage of silver in the alloy German siiver is:

  • 0%

  • 1.0%

  • 2.5%

  • 1.5%


A.

0%

Percentage of silver in the alloy German silver is 0%.  German silver, name for various alloys of copper, zinc, and nickel, sometimes also contain lead and tin. It varies in composition, the percentage of the three elements ranging approximately as follows: copper, from 50% to 61.6%; zinc, from 19% to 17.2%; nickel, from 30% to 21.1% and hence, no silver 0%.


37.

How many grams of CaC2O4 will dissolve in distilled water to make one litre of saturated solution? Solubility product of CaC2O4 is 2.5 x 10-9 mol2 litre-2 and its molecular weight is 128

  • 0.0640 gm

  • 0.0032 gm

  • 0.0128 gm

  • 0.0064 gm


D.

0.0064 gm

Ksp of CaC2O4 (a binary electrolyte) = 2.5 × 10-9

Now we know, 

Ksp = S2 (S - molar solubility)

or S = Ksp = 2.5 × 10-9 

       = 5 ×10-5 mL-1

Amount of CaC2O4 to make one litre saturated solution

= 5 × 10-5 moles ×128 g mol-1

= 0.0064 gm


38.

What would be the freezing point of aqueous solution containing 17g of C2H5OH in 1000 g of water?

  • 0.34°C

  • 0.0°C

  • -0.34°C

  • -0.69°C


D.

-0.69°C

Molality of C2H5OH (non- electrolyte solution)         = 17 gm / 46 × 1000 gm1000 gm water         = 0.369Tf = kf × m         = 1.86 × 0.369          = 0.686

Freezing point of the solution

        = 0°C - 0.686°C

        = 0.69°C


39.

The 3rd transitional series contain elements having atomic numbers from:

  • 21 to 29

  • 21 to 30

  • 20 to 30

  • 21 to 31


B.

21 to 30

The third transitional series contain elements having atomic numbers from 21 to 30.


40.

The pH of a solution is 5.0. If H+ ion concentration is decreased 100 times. Then the solution will be :

  • neutral

  • more acidic

  • basic

  • of the same acidity


A.

neutral

pH of the solution = 5.0

[H+] = 10-5 M

On decreasing the H+ ion concentration 100 times the [H+] becomes

 = 10-5100 = 10-7 M

Now pH = 7, that signifies a neutral solution.