Solution & Marking Scheme 12th Chemistry CBSE Exam 2015 (Outside) Value points. TestPaperz.com

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1 Solution & Maring Scheme 2th Chemistry CBSE Exam 205 (Outside) Que stion Value points Mars 0. AlCl 3, due to greater charge on Al X 2 Y H 3 PO 2, H 3 PO 3, H 4 P 2 O 5, H 4 P 2 O 6, H 3 PO 4, H 4 P 2 O 7, H 3 PO 5, H 4 P 2 O 8, (HPO 3 ) 3, (HPO 3 ) n (Any two) 04. 2,2 Dimethylpropan ol 05. C 6 H 5 CH 2 CH 2 Br 06. (i) As solubility of gases decreases with increase of temperature, less oxygen is available in summer in the laes / as cold water contains more oxygen dissolved. They will shrin, due to osmosis. Wt. of Ag =.5g Current = i =.5amp Molecular mass = 08 g/mol n = number of electron transferred F = C/mol t = = = s or 4.89 min At cathode: Ag + + e 08g of Ag require F.5g of Ag require Ag (s) =893.5s or 4.89 min 08. Due to comparable energies of ns & (n )d orbitals / due to presence of unpaired electrons in (n )d orbitals. In transition elements, oxidation states differ from each other by unity whereas in case of p- bloc elements, the oxidation states differ by units of two / In transition elements, the higher oxidation states are more stable for heavier elements in a group. In p bloc elements, the lower oxidation states are more stable for heavier members due to inert

2 2 pair effect. (Any one difference) 09. (i) Ammineaquadichloridoplatinum(II) [Cr(en) 3 ]Cl 3 0. (i) Zn-Hg, HCl or H 2 N NH 2 & KOH/Glycol, PCl 5 / PCl 3 / SOCl 2 (Any one) 0. (i) C 6 H 5 CHO < CH 3 CHO < HCHO 4 Methoxybenzoic acid < 4 Nitrobenzoic acid < 2,4 Dinitrobenzoic acid. W B = 5g M B = 80 g/mol W A = 50g Ps =? = = 0.0 p s = mm of Hg 2. (i) Non Stoichiometric defect F Centre / Farbe Centre (iii) NaCl is heated in an atmosphere of Na vapour / LiCl is heated in an atmosphere of Li vapour / KCl is heated in an atmosphere of K vapour. 3. A 2+ + B + A 3+ + B (n = ) Kc = 0 0 F = 96500C/mol T = 25 o C = 298K G o =? E o =? R = 8.34J/K/mol G o = 2.303RT log Kc G o = x 8.34 J/K/mol x 298K X log 0 0. G o = J/mol or J/mol G o = J/mol = nfe o = x x E o E o = = 0.59V (or any other correct method) 4. The accumulation of molecular species at the surface rather than in the bul of a solid or liquid is termed adsorption. eg: gas lie O 2, H 2, CO, Cl 2, NH 3 or SO 2 is taen in a closed vessel containing powdered charcoal Due to bond formation / interaction between adsorbent and adsorbate Physical (van der Waal s adsorption) & Chemical (Langmuir adsorption) 5. (i) Van Arel Method / vapour phase refining Zn acts as a reducing agent

3 3 (iii) As S is positive / G is more negative 6. (i) The large positive E 0 value for Mn 3+ / Mn 2+ shows that Mn 2+ (3d 5 / half filled d orbital) is much more stable than Mn 3+ Whereas Cr 3+ 3 (t 2g ) is more stable than Cr 2+ Due to d d transition / due to presence of unpaired electrons in d orbitals which absorb light in visible region (iii) 2MnO 4 + 6H C 2 O 4 2Mn H 2 O + 0CO 2 7. (i) Linage isomerism t 2 g 3 eg / Diagrammatic representation (iii) d 2 sp 3, Octahedral, 8. (i) CH 3 CH=CH 2 CH 3 CH(OH) CH 3 (iii) (or any other correct method) 8. (i) C 2 H 5 Cl + NaI C 2 H 5 I + NaCl + 2NaCl (iii) CH 3 Cl +KNO 2 CH 3 ONO + KCl 9. (i) Due to I / R effect of NO 2 group & +I / +R effect of CH 3 group or 4-nitrophenoxide ion is more stable than 4-methylphenoxide ion Due to +R effect of OH group in phenol / due to sp 2 hybridization of C atom in C OH group in phenol whereas sp 3 hybridization of C atom in C OH group in methanol. (iii) (CH 3 ) 3 C Br being a 3 o halide prefers to undergo β elimination on reacting with strong base lie NaOCH C 6 H 5 COOH

of amino than carboxyl groups are present (iii) Phosphodiester linage 23.

4 4 2. (i) and and (iii) 22. (i) Maltose ( Note: half mar for structure/s and half mar for name/s in each case) In acidic amino acid more carboxyl groups as compared to amino groups are present & In basic amino acid more number of amino than carboxyl groups are present (iii) Phosphodiester linage 23. (i) Caring nature / Generous / Sensible human approach / empathy/ concern (any two) By maing posters & displaying them in school premises / by doing role play ( or any other correct answer) (iii) Drugs which are used for the treatment of /counteract depression. eg: Rauwolfia serpentina / Barbituric acid / Equanil / Valium (Diazeparn) / Chlordiazepoxide / meprobamate / iproniazid / phenelzine (any one example) (iv) Saccharin / Aspartame / Alitame / Sucrolose / Cyclamate / L-Glucose (any one) 24. A = B = C = D = E =,, each 24. (a) (i) (iii) (b) (CH 3 ) 3 N < C 2 H 5 NH 2 < C 2 H 5 OH (c) By Hinsberg test - Add Hinsberg reagent (Benzene sulphonyl chloride) in both compounds (CH 3 ) 2 NH forms ppt insoluble in KOH while (CH 3 ) 3 N does not react,,

5 5 ( or any other correct test) 25. (a) 25. (i) Ao = 0.60 A = 0.30 when t = 30s 0.023s When Ao = 0.60 A = 0.5 when t = 60s 0.023s As for both cases is approximately same reaction is of pseudo first order Average rate during the interval sec = = = mol L S. (a) (i) Rate increases by 4 times 2 nd order (b) Reaction is 50% completed in 23. min i.e. Half-life is 23. min = = = 0.03 min t = min

26. (b) 6 (a) (i) Due to lone pair of electron on nitrogen in NH 3 Due to inert pair effect / Stability of higher oxidation state decreases down the group from S to Te / Stability of lower oxidation

6 26. (b) 6 (a) (i) Due to lone pair of electron on nitrogen in NH 3 Due to inert pair effect / Stability of higher oxidation state decreases down the group from S to Te / Stability of lower oxidation state increases down the group (iii) ClO 4 is more stable than ClO / ClO 4 is wea conjugate base than ClO (i), 26. (a) PH 3 P 4 + 3NaOH + 3H 2 O 3NaH 2 PO 2 + PH 3 (b) Xe + [PtF 6 ], Approximately same molecular size of Xe & O 2 / Comparable ionisation energies of Xe & O 2 (c) It is due to (i) low enthalpy of dissociation of F-F bond high hydration enthalpy of F. (d) (i) for bleaching wood pulp (required for manufacture of paper and rayon), cotton and textiles. In the metallurgy (extraction) of gold and platinum. (iii) In the manufacture of dyes, drugs and organic compounds such as CHCl 3, CCl 4, DDT, refrigerants (CCl 2 F 2, freon), and bleaching powder. (iv) In the preparation of poisonous gases such as phosgene (COCl 2 ), tear gas (CCl 3 NO 2 ), mustard gas (ClCH 2 CH 2 SCH 2 CH 2 Cl), etc. Mustard gas was used by Germany in World War I. (v) In sterilizing drining water. (Any one use) (e) CaF 2 + H 2 SO 4 CaSO 4 + 2HF,,,

CHEMISTRY MARKING SCHEME AJMER 2015 SET - 56/2/A. Value points

CHEMISTRY MARKING SCHEME AJMER 205 SET - 56/2/A Que Mars Value points stion 0. H 3 PO 2, H 3 PO 3, H 4 P 2 O 5, H 4 P 2 O 6, H 3 PO 4, H 4 P 2 O 7, H 3 PO 5, H 4 P 2 O 8, (HPO 3 ) 3, (HPO 3 ) n (Any two)