Board Paper of Class 12-Science 2014 Chemistry (SET 2) - Solutions

• Question 1
  Why is adsorption always exothermic? VIEW SOLUTION

• Question 2
  Name the method that is used for refining of nickel. VIEW SOLUTION

• Question 3
  Why does NO₂ dimerise? VIEW SOLUTION

• Question 4
  Based on molecular forces, what type of polymer is neoprene? VIEW SOLUTION

• Question 5
  What are the products of hydrolysis of maltose? VIEW SOLUTION

• Question 6
  Write the structure of 4-chloropentan-2-one. VIEW SOLUTION

• Question 7
  Identify the chiral molecule in the following pair:
  VIEW SOLUTION

• Question 8
  The conversion of primary aromatic amines into diazonium salts is known as __________ . VIEW SOLUTION

• Question 9
  Write the names of monomers used for getting the following polymers:
  
  (i) Terylene
  (ii) Nylon-6,6 VIEW SOLUTION

• Question 10
  Describe the roles of the following:
  (i) SiO₂ in the extraction of copper from copper matte
  (ii) NaCN in froth floatation process VIEW SOLUTION

• Question 11
  Complete the following equations:
  
  (i) $\mathrm{Ag}+{\mathrm{PCl}}_5 \to$
  (ii) ${\mathrm{CaF}}_2+{\mathrm{H}}_2{\mathrm{SO}}_4 \to$ VIEW SOLUTION

• Question 12
  Draw the structures of the following:
  
  (i) XeF₄
  (ii) HClO₄ VIEW SOLUTION

• Question 13
  (i) Write the type of magnetism observed when the magnetic moments are oppositely aligned and cancel out each other.
  (ii) Which stoichiometric defect does not change the density of the crystal? VIEW SOLUTION

• Question 14
  Define the following terms:
  
  (i) Fuel cell
  (ii) Limiting molar conductivity $\left({\wedge }_m^0\right)$ VIEW SOLUTION

• Question 15
  Write the mechanism of the following reaction:
  
  ${\mathrm{CH}}_3{\mathrm{CH}}_2\mathrm{OH} \stackrel{\mathrm{HBr}}{\to }{\mathrm{CH}}_3{\mathrm{CH}}_2\mathrm{Br}+{\mathrm{H}}_2\mathrm{O}$ VIEW SOLUTION

• Question 16
  For a chemical reaction R → P, the variation in the concentration (R) vs. time (t) plot is given as
  
  
  
  (i) Predict the order of the reaction.
  (ii) What is the slope of the curve? VIEW SOLUTION

• Question 17
  An element with density 2.8 g cm⁻³ forms of f.c.c. unit cell with edge length 4 × 10⁻⁸ cm. Calculate the molar mass of the element.
  
  (Given: N_A = 6.022 × 10²³ mol​⁻¹) VIEW SOLUTION

• Question 18
  Write the equations involved in the following reactions:
  
  (i) Reimer − Tiemann reaction
  (ii) Williamson synthesis VIEW SOLUTION

• Question 19
  Define the following terms:
  
  (i) Glycosidic linkage
  (ii) Invert sugar
  (iii) Oligosaccharides VIEW SOLUTION

• Question 20
  On the occasion of World Health Day, Dr. Satpal organized a 'health camp' for the poor farmers living in a nearby village. After check-up, he was shocked to see that most of the farmers suffered from cancer due to regular exposure to pesticides and many were diabetic. They distributed free medicines to them. Dr. Satpal immediately reported the matter to the National Human Rights Commission (NHRC). On the suggestions of NHRC, the government decided to provide medical care, financial assistance, setting up of super-speciality hospitals for treatment and prevention of the deadly disease in the affected villages all over India.
  (i) Write the values shown by
  (a) Dr. Satpal
  (b) NHRC
  (ii) What type of analgesics are chiefly used for the relief of pains of terminal cancer?
  (iii) Give an example of artificial sweetener that could have been recommended to diabetic patients. VIEW SOLUTION

• Question 21

  Account for the following:
  (i) Primary amines (R-NH₂) have higher boiling point than tertiary amines (R₃N).
  (ii) Aniline does not undergo Friedel - Crafts reactions:
  (iii) (CH₃)₂NH is more basic than (CH₃)₃N in an aqueous solution.

  
  OR

  
  Give the structures of A, B and C in the following reactions:
  
  (i) ${\mathrm{C}}_6{\mathrm{H}}_5{\mathrm{NO}}_2 \stackrel{ \mathrm{Sn} + \mathrm{HCl} }{\to } \mathrm{A} \underset{273 \mathrm{K}}{\overset{ {\mathrm{NaNO}}_2 + \mathrm{HCl} }{\to }} \mathrm{B} \stackrel{ {\mathrm{H}}_2\mathrm{O} }{\to }$
  
  (ii) ${\mathrm{CH}}_3\mathrm{CN} \stackrel{{\mathrm{H}}_2\mathrm{O}/{\mathrm{H}}^{+}}{\to } \mathrm{A} \underset{∆}{\overset{ {\mathrm{NH}}_3 }{\to }} \mathrm{B} \stackrel{ {\mathrm{Br}}_2+\mathrm{KOH} }{\to } \mathrm{C}$

  VIEW SOLUTION

• Question 22
  (a) Draw the structures of major monohalo products in each of the following reactions:
  (i)
  (ii)
  
  (b) Which halogen compound in the following pair will react faster in S_N2 reaction?
  (CH₃)₃C−Cl or CH₃−Cl VIEW SOLUTION

• Question 23
  (a) Calculate ∆rG° for the reaction
  Mg (s) + Cu²⁺ (aq) → Mg²⁺ (aq) + Cu (s)
  Given : E° _cell = + 2·71 V, 1 F = 96500 C mol⁻¹
  (b) Name the type of cell which was used in Apollo space programme for providing electrical power. VIEW SOLUTION

• Question 24
  The following data were obtained during the first order thermal decomposition of SO₂Cl₂ at a constant volume :
  SO₂Cl₂ (g) → SO₂ (g) + Cl₂ (g)

  Experiment	Time/s−1	Total pressure/atm
  1	0	0·4
  2	100	0·7

  Calculate the rate constant.
  (Given : log 4 = 0·6021, log 2 = 0·3010) VIEW SOLUTION

• Question 25
  What are emulsions? What are their different types? Give one example of each type. VIEW SOLUTION

• Question 26
  Give reasons for the following:
  (i) (CH₃)₃ P = O exists but (CH₃)₃ N = O does not.
  (ii) Oxygen has less electron gain enthalpy with negative sign than sulphur.
  (iii) H₃PO₂ is a stronger reducing agent than H₃PO₃. VIEW SOLUTION

• Question 27
  (i) Write the IUPAC name of the complex [Cr(NH₃)₄Cl₂]Cl.
  (ii) What type of isomerism is exhibited by the complex [Co(en)₃]³⁺?
              (en = ethane-1,2-diamine)
  (iii) Why is [NiCl₄]²⁻ paramagnetic but [Ni(CO)₄] is diamagnetic?
          (At. nos. : Cr = 24, Co = 27, Ni = 28) VIEW SOLUTION

• Question 28
   (a) Write the products formed when CH₃CHO reacts with the following reagents:
       (i) HCN
       (ii) H₂N−OH
       (iii) CH₃CHO in the presence of dilute NaOH
  
  (b) Give simple chemical tests to distinguish between the following pairs of compounds:
       (i) Benzoic acid and Phenol
       (ii) Propanal and Propanone

  
  OR

  
  (a) Account for the following:
       (i) Cl−CH₂COOH is a stronger acid than CH₃COOH.
       (ii) Carboxylic acids do not give reactions of carbonyl group.
  
  (b) Write the chemical equations to illustrate the following name reactions:
       (i) Rosenmund reduction
       (ii) Cannizzaro's reaction
  
  (c) Out of CH₃CH₂−CO−CH₂−CH₃ and CH₃CH₂−CH₂−CO−CH₃, which gives iodoform test? VIEW SOLUTION

• Question 29
  (a) Define the following terms :
  (i) Molarity
  (ii) Molal elevation constant (K_b)
  
  (b) A solution containing 15 g urea (molar mass = 60 g mol^–1) per litre of solution in water has the same osmotic pressure (isotonic) as a solution of glucose (molar mass = 180 g mol^–1) in water. Calculate the mass of glucose present in one litre of its solution.
   

  OR

  
  (a) What type of deviation is shown by a mixture of ethanol and acetone? Give reason.
  
  (b) A solution of glucose (molar mass = 180 g mol^–1) in water is labelled as 10% (by mass). What would be the molality and molarity of the solution?
  (Density of solution = 1.2 g mL^–1) VIEW SOLUTION

• Question 30
  (a) Complete the following equations :
  (i)  ${\mathrm{Cr}}_2{{\mathrm{O}}_7}^{2-} + 2{\mathrm{OH}}^{-} \to$
  (ii) ${{\mathrm{MnO}}_4}^{-} + 4{\mathrm{H}}^{+} + 3{\mathrm{e}}^{-} \to$
  
  (b) Account for the following :
  (i) Zn is not considered as a transition element.
  (ii) Transition metals form a large number of complexes.
  (iii) The E° value for the Mn³⁺/Mn²⁺ couple is much more positive than that for Cr³⁺/Cr²⁺ couple.

  
   OR

  
  (i) With reference to structural variability and chemical reactivity, write the differences between lanthanoids and actinoids.
  (ii) Name a member of the lanthanoid series which is well known to exhibit +4 oxidation state.
  (iii) Complete the following equation :
  ${{\mathrm{MnO}}_4}^{-} + 8{\mathrm{H}}^{+} + 5{\mathrm{e}}^{-}\to$
  (iv) Out of Mn³⁺ and Cr³⁺, which is more paramagnetic and why?
  (Atomic nos. : Mn = 25, Cr = 24) VIEW SOLUTION