2 Marks Questions

Question 12 Marks

Describe how the following conversions can be brought about (any two)?
i. Cyclohexanol to cyclohexan-1-one.
ii. Ethyl benzene to benzoic acid.
iii. Bromobenzene to benzoic acid.

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Question 22 Marks

Calculate the osmotic pressure in pascals exerted by a solution prepared by dissolving 1.0 g of polymer of molar mass 185,000 in 450 mL of water at 37°C.

Answer

It is given that:
Volume of water, V= 450 mL = 0.45 L
Temperature, T = (37+273) K = 310 K
Number of moles of the polymer, n = $\frac{1}{185000} mol$
We know that:
Osmotic pressure, $\pi=\frac{n}{V} R T$
$=\frac{1}{185000} mol \times \frac{1}{0.45} \times 8.314 \times 10^3 PaLK ^{-1} mol^{-1} \times 310 K$
= 30.98 Pa
= 31 Pa (approximately)

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Question 32 Marks

The vapour pressure of pure benzene at a certain temperature is $0.850 \ bar.$ A non$-$volatile, non$-$electrolyte solid weighing $0.5 \ g$ when added to $39.0 \ g$ of benzene $($molar mass $78\ g \ mol^{-1}). $Vapour pressure of the solution, then, is $0.845 \ bar.$ What is the molar mass of the solid substance?

Answer

The various quantities known to us are as follows:
$p _1^0=0.850 \ bar; \ p =0.845 \ bar; M _1=78 \ g \ mol ^{-1} ; w _2=0.5 \ g ; w _1=39 \ g$
Substituting these values in equation of relative lowering of vapour pressure, we get
$\frac{0.850 bar -0.845 bar }{0.850 bar }=\frac{0.5 g \times 78 gmol ^{-1}}{M_2 \times 39 g}$
Therefore, $M_{2 }= 170g \ mol^{-1}$

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Question 42 Marks

Answer the following:
(a) For a certain reaction large fraction of molecules has energy more than the threshold energy, yet the rate of reaction is very slow. Why?
(b) State a condition under which a bimolecular reaction is kinetically first-order reaction.

Answer

(i)Though the reacting large fraction of molecules may be having energy more than threshold energy, yet they may not be effective due to lack of proper orientation.
(ii) Let us consider a biomolecular reaction:
A+B → Product
Rate = k[A][B] ...(i)
When the concentration of [B] is taken in large excess that its concentration hardly change, rate law will become Rate
=k'[A]
where, k' = k[B]
The order of reaction will be equal to one.

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Question 52 Marks

What is lanthanoid contraction? What is its effect on the chemistry of the elements which follow the lanthanoids?

Answer

The decrease in atomic and ionic size with increase in atomic number among lanthanoids is called lanthanoid contraction. The elements after lanthanoids closely resemble with the elements exactly above them due to similar ionic size for example Zr and Hf have similar sizes.

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Question 62 Marks

$i.$ What type of isomerism is shown by the complex $[Cr(H_2O)_6]Cl_3?$
$ii.$ On the basis of crystal field theory, write the electronic configuration for $d^4$ ion if $\Delta_o > P.$
$iii.$ Write the hybridization and shape of $[CoF_6]^3. ($Atomic number of $Co = 27)$

Answer

$i.$ Hydration isomerism
$ii.$ Electronic configuration is tag $t_{2 g}^4$
$iii.$ Hybridization is $sp^{3}d^{2}$ and shape is octahedral.

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Chemistry 2 Marks Questions

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