4 Marks Questions

Question 14 Marks

Out of pure liquid and azeotrope showing positive deviation, Which one has a higher boiling point?

Answer

The boiling point of a pure liquid is higher as compared to azeotrope showing positive deviation.

Question 24 Marks

Read the following text carefully and answer the questions that follow:
The solutions which boil at a constant temperature like a pure liquid and possess the same composition in liquid, as well as vapour state are called azeotropes. The components of azeotropes cannot be separated by fractional distillation. Only non-ideal solutions form azeotropes. Solutions with negative deviation form maximum boiling azeotrope and the solutions with positive deviation form minimum boiling azeotrope. The boiling point of azeotrope is never equal to the boiling points of any of the components of the azeotrope.
i. The azeotropic solutions of two miscible liquids show what type of deviation from Raoult's law?
ii. The azeotropic mixture of water & HCI boils at 108.5°C. What type of deviation is shown by the solution?
Does this solution behave as ideal or non-ideal?
iii. Do ideal solutions form azeotropes?

Answer

i. The azeotropic solutions of two miscible liquids may show positive or negative deviation from Raoult's law.
ii. The solution is a non-ideal solution and shows a negative deviation from Raoult's law.
iii. No, ideal solutions don't form azeotropes. Only the non-ideal solution form azeotrope.

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Question 34 Marks

Transition metals and their many compounds act as good catalyst. Give reason.

Answer

a. The ability of transition metal ion to pass easily from one oxidation state to another and thus providing a new path to reaction with lower activation energy.
b. The surface of transition metal acts as very good adsorbent and thus provides increased concentration of reactants on their surface causing the reaction to occur.

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Question 44 Marks

Read the following text carefully and answer the questions that follow:
The f$-$block consists of elements in which $4f$ and $5f$ orbitals are progressively filled. They are placed in a separate panel at the bottom of the periodic table. The names transition metals and inner transition metals are often used to refer to the elements of d$-$and f$-$blocks respectively. The d$-$block occupies the large middle section of the periodic table flanked between s and p blocks in the periodic table. In general, the electronic configuration of the outer orbitals of these elements is $(n-1)d^{1-10}ns^{1-2}.$ The electronic configurations of outer orbitals of $Zn, Cd, Hg$ and $Cn$ are represented by the general formula $(n - 1)d^{10}ns^2.$ The transition metals and their compounds also exhibit catalytic property and paramagnetic behaviour. Transition metal also forms an alloy. An alloy is a blend of metals prepared by mixing the components. Alloys may be homogeneous solid solutions in which the atoms of one metal are distributed randomly among the atoms of the other.
$i.$ Transition metals form alloys. Justify?
$ii.$ Why do transition elements exhibit higher enthalpies of atomization?
$iii.$ Transition metals and many of their compounds show paramagnetic behaviour. Give reason.

Answer

$i.$ The transition metals are quite similar in size and, therefore, the atoms of one metal can substitute the atoms of other metal in its crystal lattice. Thus, on cooling a mixture solution of two or more transition metals, solid alloys are formed.
$ii.$ The high enthalpies of atomization are due to a large number of unpaired electrons in their atoms. Therefore, they have stronger interatomic interactions and hence, stronger bonding between atoms.
$iii.$ Transition elements and many of their compounds are paramagnetic, i.e., they are weakly attracted by a magnetic field. This is due to the presence of unpaired electrons in atoms, ions or molecules. The paramagnetic character increases as the number of unpaired electrons increases.

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Chemistry 4 Marks Questions

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