Chemistry-1997-Set III

Q 2 Which one out of O+2 and O-2 is more stable.
Ans. 1 O+2 is more stable because its bond order is higher than O-2.

Q 5 How is the unit of molar conductivity arrived at?
Ans. 2 Molar conductivity (m) = K x 1000 / cm
(m) = ohm-1 cm-1 / moles/cm3

Q 6 Which one among the following is strongest oxidising agent : ClO4-, BrO4-, IO4-
Ans. 3 BrO4-

Q 12 The solubility of Ba(OH)2.8H2O in water at 288k is 5.6 g per 100 g of water. What is the molality of the hydroxide ions in the saturated solution of barium hydroxide at 288k? (Atomic mass : Ba=137, O=16, h=1)
Ans. 4 WB = 5.6 g , WB = 100 gm = WB. 100 / MB.WB
= 5.6 x 1000 / 315 x 100 = 0.17
Molarity of Ba(OH) 2.8 H2O = 0.17
Since, one mole Ba(OH) 2.8 H2O will finish two moles of OH- ions.
Molarity of OH- ion = 2 x 0.17 = 0.34 m

Q 16 Consider the following data for the reaction : A + B —–> Products.
Run Initial Conc Initial Conc Initial rate(mols-1)
A B
1 0.10M 1.0M 2.1×10-3
2 0.20M 1.0M 8.4×10-3
3 0.20M 2.0M 8.4×10-3

Determine the order of reaction with respect to A and with respect to B, and the over all order of the reaction.
Ans. Divide Expt. No. (i) and (ii) K [A] [B] = rate of reaction
K[0.20] [1.0] /K[0.10] [1.0] = 8.4 x 10-3/2.1 x 10-3
2 =4 or 2=22 or = 2
So order w.r.t A=2
From Expt.No.(ii) and (iii) it is clear that rate of reaction does not change
in concentration of B, So order W.r.t. B is 1, i.e Rate = k[A]2 [B]o
over all order of reaction = 2

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