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Rearrange the following (I to IV) in the order of increasing masses and choose answer from (1), (2), (3) and (4) (Atomic mass : N=14, O=16 Cu = 63)

I. 1 molecule of oxygen

II. 1 atom of nitrogen

III. 1 x 10-10g molecular weight of oxygen

IV. 1 x 10-10g weight of copper

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Explanation

1 molecule of oxygen = 32 a.m.u=32 x 1.66x 10-24g

1 atom of nitrogen =14 a.m.u=14 x 1.66x 10-24g

1 x 10-10 g molecular weight of oxygen =  avg no of molecules of oxygen is 32 gram.so wt of given no is 

 32 x 10-14g

1 x 10-10g atomic weight of copper = 63.5 x 10-14g

So, order is II < I <III <IV

The ratio of number of atoms in 2.2g CO2 and 1.7g NH3 is 

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Explanation

No. of atoms in 2.2 g CO2(n1) = 2244×3×NA

No. of atoms in 1.7g NH3(n2) =1.717×4×NA

n1n2=38

How many moles of FeC2O4 are required to reduce one mole of KMnO4 in acidic medium?

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Explanation

 

3KMnO4+5FeC2O4+24H+5Fe3++10CO2+3Mn2++3K++12H2O\

  1. Ferrous is oxidized to ferric state
  2. Carbon and hydrogen are converted to CO2 and H2O
  3. All the metallic ions are converted to sulphates
  4. Write the equation keeping in mind that the valency of of iron in ferric state is 3, that of K and Mn is one and two respectively as
  5. FeC2O4 + KMnO4 + H2SO4 = K2SO4 + MnSO4 + Fe(SO4)3 + H2O + CO2
  6. FeC2O4 is oxidized and KMnO4 is reduced. Hence the main reaction is
  7. Fe2+ → Fe3+ (removal of 1 electron)

Mn7+ → Mn 2+ (addition of 5 electrons)

In order to balance multiply (Fe2+ → Fe3+) by 5

Now you know that there should be 5 FeC2O4 molecules. Write that and balance the rest.

Which of the following pairs of gases contains the same number of molecules:-

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Explanation

Mole (n) = Weight Molecular weight=No. of moleculesNA

The number of ions present in 2L of a solution of 1.6M K4[Fe(CN)6] is:-

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Explanation

No. of molecules of  K4[Fe(CN)6] = 1.6 x 2 x 6 x 1023

No. of ions = 5 x 1.6 x 2 x 6 x 1023

= 9.6 x 1024

The mass of CO2 that shall be obtained by heating 10 kg of 80% pure lime stone (CaCO3) is:-

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Explanation

CaCO3(S)  CO2(g) + CaO(s)

100 kg 44 kg

80100×10kg 44100×80100×10=3.52 kg

When 1L of CO2 is heated with graphite,the volume of the gases collected is 1.8L. What will be the number of moles of CO produced at STP?

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Explanation

The reaction is: C(s) + CO2(g) → 2CO(g). Initially, there are 1 mol of CO2. After the reaction, the total volume is 1.8 L, which corresponds to 1.8 mol of gaseous product (assuming STP). Since 1 mol of CO2 produces 2 mol of CO, the moles of CO produced is 0.0714 mol.

At STP the moles of oxygen atoms in 2.8 L of CO2 gas is:-

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Explanation

Moles of CO2volume of gas22.4=2.822.4=0.125 mol

moles of oxygen atom in given CO2 = 0.125 x 2=0.25 mol

Which of the following relation is incorrect:-

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Explanation

1 mol N-3 ion 1 x 10 mol e

1 mol O-2 ion 1 x 10 mol e= 6.023x10-24e-

1 mol CH4 1 x 10 mol proton

1 mol H21 x 10 mol proton

Mass of sucrose C12H22O11 produced by mixing 84 gm of carbon, 12gm of hydrogen and 56L. O2 at 1atm & 273 K according to give reaction, is C(s) + H2(g) +O2(g)  C12H22O11 (s)

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Explanation

Balanced Equation:

24C + 22H2 + 11O2 -> 2C12H22O11

moles for reaction: 

7(84/12), 6(12/2), (56/22.4)

dividing by coefficients in balanced equation & comparing: 

7/24, 6/22,  (56/22.4)/11 

0.29, 0.27, 0.22

Oxygen is the limiting reagent. So, weight of sucrose obtained = 0.22 * 2(coefficient for sucrose in reaction) * 342(sucrose molecular weight) = 155.5g

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