10 g of MgCO3 decomposes on heating to 0.1 mole CO2 and 4 g MgO.

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 Multiple Choice QuestionsMultiple Choice Questions

61.

Molarity is defined as

  • the number of moles of solute dissolved in 1 dm3 of the solution

  • the number of moles of solute dissolved in 1 kg of solvent

  • the number of moles of solute dissolved in 1 dm3 of the solvent

  • the number of moles of solute dissolved in 100 ml of the solvent


62.

The molality of solution containing 15.20 g of urea, (molar mass = 60) dissolved in 150 g of water is

  • 1.689 mol kg-1

  • 0.1689 mol kg-1

  • 0.5922 mo kg-1

  • 0.2533 mol kg-1


63.

For which among the following equimolar aqueous solutions Van't Hoff factor has the lowest value?

  • Aluminium chloride

  • Potassium sulphate

  • Ammonium chloride

  • Urea


64.

The molality of the 3M solution of methanol if the density of the solution is 0.9 g cm-3 is

  • 3.73

  • 3.0

  • 3.33

  • 3.1


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65.

10 g of MgCO3 decomposes on heating to 0.1 mole CO2 and 4 g MgO. The percent purity of MgCO3 is

  • 24%

  • 44%

  • 84%

  • 74%


C.

84%

Since, MgCO3  MgO + CO2

Mole ratio 1 : 1 : 1

Mass ratio 84 : 40 : 44

Given values 10 gm - 4 gm 0.1 mol = 4.4 g ( n = wm)

(i) 84 gm of MgCO3 give MgO = 40 gm

    10 gm of MgCO3 give MgO = 40 × 1084 = 4.76 gm

Thus, MgO obtained is less by = 4.76 - 4.0 = 0.76 gm

(ii) 84 gm of MgCO3 give CO2 = 44 gm

     10 gm of MgCO3 give CO244 × 1084 = 5.23 gm

Thus, CO2 obtained is less by 5.23 - 4.4 = 0.84 gm

Total short = 0.76 + 0.84 = 1.59 ≅ 1.60

   10 gm of MgCO3 give less products by = 1.60 gm

  100 gm of MgCO3 give less products by = 1.600 gm

Hence, MgCO3 = 100 - 16 = 84%


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66.

The compound Na2CO3 . x H2O has 50% H2O by mass. The value of "x" is

  • 4

  • 5

  • 6

  • 8


67.

The volume of oxygen liberated at STP from 15 mL of 20 volume H2O2 is

  • 100 mL

  • 200 mL

  • 300 mL

  • 400 mL


68.

Calculate the molality of a solution that contains 51.2 g of naphthalene (C10H8) in 500 mL of carbon tetrachloride. The density of CCl4 is 1.60 g/mL

  • 0.250 m

  • 0.500 m

  • 0.750 m

  • 0.840 m


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69.

When 2.46 gm of a hydrated salt (MSO4xH2O) is completely dehydrated, 1.20 gm of anhydrous salt is obtained. If the molecular weight of anhydrous salt is 120 gm mol-1, what is the value of x?

  • 2

  • 7

  • 4

  • 6


70.

An organic compound contains 90% carbon and 10% hydrogen by mass. Its empirical formula is

  • C2H4

  • C3H6

  • C3H8

  • C3H4


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