Class 12th Chemistry 2018 Set3 Delhi Board Paper Solution

Write the coordination number and oxidation state of Platinum in the complex [Pt(en)₂Cl₂].

Analysis shows that FeO has a non-stoichiometric compositions with formula Fe_0.95O. Give reason.

Out of Chlorobenzene and benzyl chloride, which one gets easily hydrolysed by aqueous NaOH and why?

Write the IUPAC name of the following:

CO(g) and H₂(g) react to give different products in the presence of different catalysts. Which ability of the catalyst is shown by these reactions?  

Among the hydrides of Group-15 elements,which have the 

(a) Lowest boiling point?

(b) maximum basic character?

(c) highest bond angle?

(d) maximum reducing character?

Calculate the freezing point of a solution containing 60g of glucose (Molar Mass = 180g mol-1) in 250g of water.

(K_f of water = 1.86K kg mol-1)

How do you convert the following:

(a) Ethanal to Propanone

How do you convert the following:

(b) Toluene to Benzoic acid 

Account for the following:

Aromatic carboxylic acids do not undergo Friedel-Crafts reaction.

Account for the following:

pK_a value of 4-nitrobenzoic acid is lower than that of benzoic acid.

Complete and balance the following chemical equations:

(a) Fe2+    +   MnO-₄   +   H+  → 

(b) MnO-₄    +   H₂O   +   I-    → 

For the reaction

     2N₂O₅(g)  →  4NO₂(g)   +    O₂(g) ,

the rate of formation of NO_2(g) is 2.8X10-3Ms-1. Calculate the rate of disappearance of N₂O₅(g).

 Identify the chiral molecule in the following pair:  

Write the structure of the product when chlorobenzene is treated with methyl chloride in the presence of sodium metal and dry ether.

Write the structure of the alkene formed by dehydrohalogenation of 1-bromo-1-methylcyclohexane with alcoholic KOH 

A first order reaction is 50 % completed in 40 minutes at 300 K and in 20 minutes at 320 K. Calculate the activation energy of the reaction.

(Given : log 2 = 0.3010, log 4 = 0.6021, R = 8.314 JK–1 mol–1)

An element 'X' (At. mass = 40g mol-1) haveing f.c.c. structure, has unit cell edge length of 400 pm. Calculate the density of 'X' and the number of unit cells in 4 g of 'X' . (N_A = 6.022 X 1023 mol-1) 

Give reasons for the following:

Measurement of osmotic pressure method is preferred for the determination of molar masses or macromolecules such as proteins and polymers. 

Give reasons for the following:

Aquatic animals are more comfortable in cold water than in warm water.

Give reasons for the following:

Elevation of boiling point of 1 M KCI solution is nearly double than that of 1 M sugar solution.

What happens when: 

A freshly prepared precipitate of Fe(OH)₃ is shaken with a small amount of FeCl₃ solution.

What happens when:  

Persistent dialysis of a colloidal solution is carried out ? 

What happens when: 

An emulsion is centrifuged ?

Write the chemical reactions involved in the process of extraction of Gold. Explain the role of dilute NaCN and Zn in this process. 

(A), (B) and (C) are three non-cyclic functional isomers of a carbonyl compound with milecular formula C₄H₈O. Isomers (A) and (C) give positive Tollens' test whereas isomer (B) does not give Tollens' test but give positive Iodoform test. Isomers (A) and (B) on reduction with Zn(Hg)/conc. HCl give the same product (D).

(a) Write the structure of (A), (B), (C) and (D).

(b) Out of A), (B), and (C) isomers, which one is least reactive towards addition of HCN?

Why is bithional added to soap?

What is tincture of iodine ? What is its use ?

Among the following, which one acts as a food preservative?

Aspartume,  Asprin,  Sodium Benzoate,  Paracetamol. 

Write the formulas for the following coordination compounds:

Iron(III) hexacyanoferrate(II)

What type of isomerism is shown by the complex [Co(NH₃)₅Cl]SO₄? 

Write the hybridisation and number of unpaired electrons in the complex [CoF₆]3- . (Atomic No. of Co =27)

Define the following with an example of each:Polysaccharides 

Define the following with an example of each:Denatured protein 

Define the following with an example of each:Essential amino acids

Write the product when D-glucose reacts with conc. HNO₃? 

Amino acids show amphoteric behaviour. Why?

Write one difference between α-helix and β-pleated structures of proteins. 

Write the structures of the main products in the following reactions:

Give reasons :

Eº value for Mn3+/Mn2+ couple is much more positive than that for Fe3+/Fe2+.

Give reasons :

Iron has higher enthalpy of atomization than that of copper. 

Give reasons :

Sc3+ is colourless in aqueous solution whereas Ti3+ is coloured. 

Shyam went to a grocery shop to purchase some food items. The shopkeeper packed all the item in polythene bags and gave them to Shyam. But Shyam refused to accept the polythese bags and asked the shopkeeper to pack the items in paper bags. He informed the shopkeeper about the heavy penalty imposed by the government for using polythene bags. The shopkeeper promised that he would use paper bags in future in place of polythene bags. Answer the following :

(a) Write the values (at least two) shown by Shyam

(b) Write one structural difference between low-density polythene and high-density polythene

(c) Why did Shyam refuse to accept the items in polythene bags ?

(d) What is a biodegradable polymer ? Give an example.

Write the reactions involved in the following:Hofmann bromamide degradation reaction

Write the reactions involved in the following:Diazotisation 

Write the reactions involved in the following:Gabriel phthalimide synthesis 

Give reasons:

(CH₃)₂NH is more basic than (CH₃)₃N in an aqueous solution 

Give reasons: 

Aromatic diazonium salts are more stable than aliphatic diazonium salts. 

Write the structures of the main products of the following reactions:

Give a simple chemical test to distinguish between Aniline and N,N-dimethylaniline. 

Arrange the following in the increasing order of their pKb values :

C₆H₅NH₂,             C₂H₅NH₂,               C₆H₅NHCH₃ 

Give reasons:

H₃PO₃ undergoes disproportionation reaction but H₃PO₄ does not.

Give reasons: 

When Cl₂ reacts with excess of F₂, ClF₃ is formed and not FCl₃.

Why is dioxygen a gas but sulphur a solid?

Draw the structures of the following : XeF₄

Draw the structures of the following : HClO₃

When concentrated sulphuric acid was added to an unknown salt present in a test tube a brown gas (A) was evolved. This gas intensified when copper turnings were added to this test tube. On cooling, the gas (A) changed into a colourless solid (B)

(i) Identify (A) and (B)

(ii) Write the structures of (A) and (B)

(iii) When does gas (A) change to solid on cooling ?

Arrange the following in the decreasing order of their reducing character

HF,   HCl,   HBr,   HI 

Complete the following reaction :

XeF₄       +     SbF₅    →

Write the cell reaction and calculate the e.m.f. of the following cell at 298K:

Sn (s) | Sn2+ (0.004 M) || H+ (0.020 M) | H₂ (g) (1 bar) | Pt (s)

(Given : E0 _Sn2+ _{/ Sn}  = 0.14) 

Give reasons :

On the basis of E0 values, O₂ gas should be liberated at anode but it is Cl₂ gas which is liberated in the electrolysis of aqueous NaCl.

Give reasons : 

Conductivity of CH₃COOH decreases on dilution.

For the reaction,

2 AgCl (s) + H₂ (g) (1 atm) ⎯⎯→ 2Ag (s) + 2H+ (0.1 M) + 2Cl– (0.1 M)

ΔGº = – 43600 J at 25ºC

Calculate the e.m.f. of the cell

[log 10–n = –n] 

Define fuel cell and write its two advantages.