The number of grams/ weight of NH4Cl required to be added to 3 li

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 Multiple Choice QuestionsMultiple Choice Questions

241.

Which one of the following is not a unit of energy?

  • lit-atm

  • Kg m2s-2

  • Nm

  • kg ms-2


242.

Acccording to significant figure convention the result obtained by adding 12.11, 18.0 and 1.012 is

  • 31.12

  • 31.1

  • 31

  • 31.122


243.

What is the weight (in gram) of Na2CO3 (molar mass = 106) present in 250 mL of its 0.2 M solution? 

  • 0.53

  • 5.3

  • 1.06

  • 10.6


244.

An organic compound having C, H and O has 13.13% H, 52.14%C and 34.73 % 0. Its molar mass is 46.068 g. What are its empirical and molecular formulae?

  • C2H6O, C4H12O2

  • C2H6O, CH3O

  • C2H6O, C2H6O

  • C2H6O, C3H9O4


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245.

The number of grams/ weight of NH4Cl required to be added to 3 litres of 0.01 M NH3 to prepare the buffer of pH = 9.45 at temperature 298 K (Kb for NH3 is 1.85 × 10-5)

  • 0.354 gm

  • 4.55 gm

  • 0.455 gm

  • 3.55 gm


A.

0.354 gm

 pOH= pKb + logNH4Cl[NH3]pOH = -log Kb + log [NH4Cl][NH3]    (pKb = -log Kb)Also, pOH= 14 - pH= 14 - 9.45 = 4.55 and log NH4Cl[NH3] Kb = log 3  0.470Thus, log 1014 - (log 109 + log 3) log NH4Cl[NH3].Kb= log 1014109 × 3 = log [NH4Cl][NH3].Kb= 1014109 × 3 = [NH4Cl][NH3].Kb= 1014 × [NH3]. Kb109 × 3= [NH4Cl] = 1014109 × 3 × 0.01 × 1.85 ×10-5= [NH4Cl] = 0.345 gm


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246.

A 6% solution of sucrose C22H22O11 is isotonic with 3% solution of an unknown organic substance. The molecular weight of unknown organic substance will be

  • 684

  • 171

  • 100

  • 342


247.

Commercially available H2SOis 98 g by H2SO4 and 2g by weight of water. It's density is 1.38 g cm-3. Calculate the molality (m) of  H2SO4 (molar mass of  H2SO4  is 98 g mol-1). 

  • 500 m

  • 20 molal

  • 50 m

  • 200 m


248.

In order to oxidise a mixture of one mole of each of FeC2O4, Fe2(C2O4)3, FeSO4 and Fe2(SO4)3 in acidic medium, the number of moles of KMnO4 required is:

  • 1.5

  • 3

  • 2

  • 1


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249.

The vapour pressures of pure liquids A and B are 400 and 600 mm Hg, respectively at 298 K. On mixing the two liquids, the sum of their initial volumes is equal to the volume of the final mixture. The mole fraction of liquid B is 0.5 in the mixture. The vapour pressure of the final solution, the mole fractions of components A and B in vapour phase, respectively are:

  • 500 mm Hg, 0.4, 0.6

  • 450 mm Hg, 0.4, 0.6

  • 500 mm Hg, 0.5, 0.5

  • 450 mm Hg, 0.5, 0.5


250.

What would be the molality of 20% (mass / mass) aqueous solution of KI? (molar mass of KI = 166 g mol-1)

  • 1.08

  • 1.35

  • 1.51

  • 1.48


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