Chemistry
- Given below are two statements :Statement I : [Co(NH_3)_6]^3+ is a homoleptic complex whereas [Co(NH_3)_4Cl_2]^+ is a heteroleptic complex.Statement II : Complex [Co(NH_3)_6]^3+ has only one kind of ligands but [Co(NH_3)_4Cl_2]^+ has more than one ki… Answer: 2. Both Statement I and Statement II are true. Key idea: a homoleptic complex has only one kind of ligand; a heteroleptic complex ha... 1
- The pair of lanthanoid ions which are diamagnetic is Answer: 2. Ce⁴⁺ and Yb²⁺ Key idea: diamagnetic means no unpaired electrons, so 4f⁰ or 4f¹⁴ . mathrmCe⁴⁺ : 4f⁰ ; mathrmYb²⁺ : 4f¹⁴ . Both dia... 1
- Consider the following reaction in a sealed vessel at equilibrium with concentrations of N_2 = 3.0×10^-3 M, O_2 = 4.2×10^-3 M and NO = 2.8×10^-3 M.2NO_(g) ⇌ N_2(g) + O_2(g)If 0.1 mol L^-1 of NO_(g) is taken in a closed vessel, what will be degree of… Answer: 1. 0.717 Key idea: get K_c from the first data set, then use it for the new mixture. K_c=[N₂][O₂]/[NO]²=frac(3.0×10⁻³)(4.2×10⁻³)(2.8... 1
- For the given reaction:[scheme: ring-C(H)=CH-ring KMnO_4/H^+ 'P' (major product), see figure]'P' is Answer: 3. [structure: ring-COOH] Key idea: hot or acidic KMnO₄ cleaves a C=C bond and oxidises each fragment fully to the carboxylic acid.... 1
- Identify the major product C formed in the following reaction sequence :CH_3-CH_2-CH_2-I NaCN A [Partial hydrolysis]OH^- B [Br_2]NaOH C (major) Answer: 2. propylamine Key idea: follow each step. CH₃CH₂CH₂I+NaCN→ CH₃CH₂CH₂CN (A, butanenitrile). Partial hydrolysis with OH^- gives CH₃CH... 1
- The products A and B obtained in the following reactions, respectively, are3ROH + PCl_3 → 3RCl + AROH + PCl_5 → RCl + HCl + B Answer: 1. H₃PO₃ and POCl₃ Key idea: phosphorus halides convert ROH into RCl, and the phosphorus part ends as an acid or oxychloride. 3ROH+P... 1
- During the preparation of Mohr's salt solution (Ferrous ammonium sulphate), which of the following acid is added to prevent hydrolysis of Fe^2+ ion? Answer: 1. dilute sulphuric acid Key idea: mathrmFe²⁺ salts hydrolyse in water, so a little acid is added, and it must not oxidise mathrmFe²... 1
- Given below are certain cations. Using inorganic qualitative analysis, arrange them in increasing group number from 0 to VI.A. Al^3+ B. Cu^2+ C. Ba^2+ D. Co^2+ E. Mg^2+Choose the correct answer from the options given below: Answer: 2. B, A, D, C, E Key idea: group numbers in qualitative analysis. mathrmCu²⁺ : Group II ( H₂S in acid). mathrmAl³⁺ : Group III ( NH₄... 1
- Mass in grams of copper deposited by passing 9.6487 A current through a voltmeter containing copper sulphate solution for 100 seconds is:(Given : Molar mass of Cu : 63 g mol^-1, 1F = 96487 C) Answer: 3. 0.315 g Key idea: Q=It , then use Faraday's law for mathrmCu²⁺+2e^-→ Cu . Q=9.6487×100=964.87 C, so moles of e^- = 964.87/96487 =... 1
- The plot of osmotic pressure () vs concentration (mol L^-1) for a solution gives a straight line with slope 25.73 L bar mol^-1. The temperature at which the osmotic pressure measurement is done is:(Use R = 0.083 L bar mol^-1 K^-1) Answer: 2. 37 ^° C Key idea: Π=CRT , so the slope of Π vs C is RT . T=25.73/0.083=310\ K=37^°C Option 2. (310 is in kelvin, not ^° C, so opt... 1
- A compound X contains 32% of A, 20% of B and remaining percentage of C. Then, the empirical formula of X is :(Given atomic masses of A = 64; B = 40; C = 32 u) Answer: 3. ABC₃ Key idea: empirical formula from percentage: divide by atomic mass, then by the smallest value. C% = 100 - 32 - 20 = 48. Ele... 1
- The energy of an electron in the ground state (n = 1) for He^+ ion is -x J, then that for an electron in n = 2 state for Be^3+ ion in J is : Answer: 2. -x Key idea: for hydrogen-like ions E_n=-E₁(H) Z²/n² . For He^+ (Z=2), n=1: -x=-4E₀ , so E₀=x/4 . For mathrmBe³⁺ (Z=4), n=2: E=-E... 1
- Fehling's solution 'A' is Answer: 2. aqueous copper sulphate Key idea: Fehling's solution is prepared as two separate solutions. Fehling's A: aqueous copper sulphate.... 1
- Arrange the following elements in increasing order of electronegativity:N, O, F, C, SiChoose the correct answer from the options given below: Answer: 2. Si < C < N < O < F Key idea: electronegativity increases across a period and decreases down a group. Pauling values: Si 1.8 < C 2... 1
- Intramolecular hydrogen bonding is present in Answer: 2. [structure: 2-nitrophenol (NO2 and OH on adjacent carbons), see figure] Key idea: intramolecular H-bonding needs the H-donor (-OH... 1
- Activation energy of any chemical reaction can be calculated if one knows the value of Answer: 1. rate constant at two different temperatures. Key idea: from the Arrhenius equation, logk₂/k₁=E_a/2.303R(1/T₁-1/T₂) . Knowing k at... 1
- Which plot of ln k vs 1/T is consistent with Arrhenius equation? Answer: 1. [graph option 1, see figure] Key idea: ln k=ln A-E_a/R·1/T , a straight line with negative slope -E_a/R and positive intercept ln... 1
- In which of the following processes entropy increases?A. A liquid evaporates to vapour.B. Temperature of a crystalline solid lowered from 130 K to 0 K.C. 2NaHCO_3(s) → Na_2CO_3(s) + CO_2(g) + H_2O_(g)D. Cl_2(g) → 2Cl_(g)Choose the correct answer from… Answer: 4. A, C and D Key idea: entropy rises with disorder, i.e. when more gas or more particles are formed. A: liquid to vapour, disorder... 1
- Match List I with List II.List I (Complex): A. [Co(NH_3)_5(NO_2)]Cl_2 B. [Co(NH_3)_5(SO_4)]Br C. [Co(NH_3)_6][Cr(CN)_6] D. [Co(H_2O)_6]Cl_3List II (Type of isomerism): I. Solvate isomerism II. Linkage isomerism III. Ionization isomerism IV. Coordinat… Answer: 2. A-II, B-III, C-IV, D-I Key idea: match each complex to the isomerism it can show. A, [Co(NH₃)₅(NO₂)]Cl₂ : NO₂^- is ambidentate, s... 1
- Given below are two statements :Statement I : Both [Co(NH_3)_6]^3+ and [CoF_6]^3- complexes are octahedral but differ in their magnetic behaviour.Statement II : [Co(NH_3)_6]^3+ is diamagnetic whereas [CoF_6]^3- is paramagnetic.In the light of the abo… Answer: 2. Both Statement I and Statement II are true. Key idea: the ligand field strength decides pairing in mathrmCo³⁺ ( d⁶ ). NH₃ is a st... 1
- 'Spin only' magnetic moment is same for which of the following ions?A. Ti^3+ B. Cr^2+ C. Mn^2+ D. Fe^2+ E. Sc^3+Choose the most appropriate answer from the options given below: Answer: 2. B and D only Key idea: μ=√(n(n+2)) BM, so equal unpaired electrons give equal moment. mathrmTi³⁺ ( d¹ ): 1 mathrmCr²⁺ ( d⁴ ): 4 m... 1
- The E^° value for the Mn^3+/Mn^2+ couple is more positive than that of Cr^3+/Cr^2+ or Fe^3+/Fe^2+ due to change of Answer: 4. d⁴ to d⁵ configuration Key idea: a high E^° for M³⁺/M²⁺ means M³⁺ is easily reduced to a very stable M²⁺ . mathrmMn³⁺ is d⁴ ; on... 1
- The Henry's law constant (K_H) values of three gases (A, B, C) in water are 145, 2×10^-5 and 35 kbar, respectively. The solubility of these gases in water follow the order: Answer: 3. B > C > A Key idea: by Henry's law p=K_Hx , so a larger K_H means lower solubility. K_H : B ( 2×10⁻⁵ ) < C (35) < A (145) kbar. S... 1
- Given below are two statements:Statement I : The boiling point of three isomeric pentanes follows the ordern-pentane > isopentane > neopentaneStatement II : When branching increases, the molecule attains a shape of sphere. This results in smaller sur… Answer: 2. Both Statement I and Statement II are correct. Key idea: among isomers, more branching means a more spherical shape and a lower b... 1