#neet
- A first order reaction has a specific reaction rate of 10^-2\ sec^-1. How much time will it take for 20 g of the reactant to reduce to 5 g ? Answer: 1. 138.6 sec Key idea: first-order integrated rate law t=2.303/kloga/a-x . t=dfrac2.30310⁻²log20/5=230.3×0.602=138.6\ s . Check: 20... 1
- Which one of the following pairs of species have the same bond order ? Answer: 2. CN^-, CO Key idea: compare bond orders from molecular orbital theory (isoelectronic species have equal bond orders). CN^- and CO... 1
- In which pair of ions both the species contain S-S bond ? Answer: 1. S₄O₆²⁻, S₂O₃²⁻ Key idea: draw the structures. mathrmS₄O₆²⁻ (tetrathionate): has an S-S bond in the chain O₃S-S-S-SO₃ . mathrmS₂O₃... 1
- Concentration of the Ag^+ ions in a saturated solution of Ag_2C_2O_4 is 2.2 × 10^-4 mol L^-1. Solubility product of Ag_2C_2O_4 is : Answer: 3. 5.3 × 10⁻¹² Key idea: Ag₂C₂O₄ ⇌ 2Ag^+ + C₂O₄²⁻ , K_sp=[Ag^+]²[C₂O₄²⁻] . [C₂O₄²⁻]=1/2[Ag^+]=1.1×10⁻⁴ M. K_sp=(2.2×10⁻⁴)²×1.1×10⁻⁴=... 1
- Ionic mobility of which of the following alkali metal ions is lowest when aqueous solution of their salts are put under an electric field ? Answer: 3. Li Key idea: in aqueous solution ionic mobility falls with greater hydration, and smaller ions hydrate more. Hydrated size order... 1
- A gas is allowed to expand in a well insulated container against a constant external pressure of 2.5 atm from an initial volume of 2.50 L to a final volume of 4.50 L. The change in internal energy Δ U of the gas in joules will be : Answer: 2. -505 J Key idea: well insulated means adiabatic, so q = 0 and Δ U = w . w=-p_extΔ V=-2.5\ atm×(4.50-2.50)\ L=-5\ L atm . Taking 1... 1
- The reason for greater range of oxidation states in actinoids is attributed to : Answer: 2. 5f, 6d and 7s levels having comparable energies Key idea: a wide range of oxidation states needs electrons from orbitals of simil... 1
- The most suitable method of separation of 1 : 1 mixture of ortho and para-nitrophenols is : Answer: 3. Steam distillation Key idea: o-nitrophenol is steam volatile, p-nitrophenol is not. o-Nitrophenol has intramolecular hydrogen bon... 1
- The correct order of the stoichiometries of AgCl formed when AgNO_3 in excess is treated with the complexes : CoCl_3.6NH_3, CoCl_3.5NH_3, CoCl_3.4NH_3 respectively is : Answer: 2. 3 AgCl, 2 AgCl, 1 AgCl Key idea: only ionisable (outside the coordination sphere) chloride precipitates with AgNO₃ . CoCl₃·6NH₃ =... 1
- Correct increasing order for the wavelengths of absorption in the visible region for the complexes of Co^3+ is : Answer: 4. [Co(en)₃]³⁺, [Co(NH₃)₆]³⁺, [Co(H₂O)₆]³⁺ Key idea: stronger ligand field means a larger splitting Δ_o , which means light of highe... 1
- Which one is the most acidic compound ? Answer: 3. [structure: 2,4,6-trinitrophenol] Key idea: electron-withdrawing groups stabilise the phenoxide ion and increase acidity. 2,4,6-T... 1
- Which of the following pairs of compounds is isoelectronic and isostructural ? Answer: 2. IBr₂^-, XeF₂ Key idea: isoelectronic means equal number of valence electrons, isostructural means same shape. XeF₂ : 8 + 14 = 22... 1
- Which of the following reactions is appropriate for converting acetamide to methanamine ? Answer: 1. Hoffmann hypobromamide reaction Key idea: Hoffmann bromamide reaction removes one carbon from an amide to give a primary amine. C... 1
- Of the following, which is the product formed when cyclohexanone undergoes aldol condensation followed by heating ? Answer: 1. [structure: 2-cyclohexylidenecyclohexanone] Key idea: aldol condensation = aldol addition followed by loss of water on heating, g... 1
- Which of the following statements is not correct ? Answer: 3. Denaturation makes the proteins more active. Key idea: denaturation destroys the 3-D structure. On denaturation (heat, acid), sec... 1
- Which one is the correct order of acidity ? Answer: 1. CHequiv CH > CH₃-Cequiv CH > CH₂=CH₂ > CH₃-CH₃ Key idea: acidity of a C-H bond increases with the s-character of carbon. Ethyne (... 1
- Extraction of gold and silver involves leaching with CN^- ion. Silver is later recovered by : Answer: 3. displacement with Zn Key idea: Ag is recovered from the cyanide complex by a more electropositive metal. 2[Ag(CN)₂]^- + Zn → [Zn(... 1
- The correct statement regarding electrophile is : Answer: 3. Electrophile can be either neutral or positively charged species and can form a bond by accepting a pair of electrons from a nucl... 1
- Consider the reactions :X\ (C_2H_6O) Cu/573\ K A [Ag(NH_3)_2]^+,\ ^-OH,Δ Silver mirror observed; A ^-OH,Δ Y; A NH_2-NH-C(=O)-NH_2 ZIdentify A, X, Y and Z Answer: 2. A-Ethanal, X-Ethanol, Y-But-2-enal, Z-Semicarbazone. Key idea: C₂H₆O with Cu/573 K dehydrogenation means a primary alcohol. X = e... 1
- The IUPAC name of the compound OHC-CH(CH_3)-C(=O)-CH=CH-CH_3 (drawn in skeletal form) is ______. Answer: 4. 3-keto-2-methylhex-4-enal Key idea: the principal functional group is the aldehyde (-CHO), which gets C-1. Chain: OHC(1)-CH(CH₃)(... 1
- Which is the incorrect statement ? Answer: 3. Frenkel defect is favoured in those ionic compounds in which sizes of cation and anions are almost equal. Key idea: Frenkel defec... 1
- A decrease in blood pressure/volume will not cause the release of : Answer: 1. Atrial Natriuretic Factor Key idea: A fall in blood pressure or volume triggers hormones that raise it; ANF does the opposite. Lo... 1
- Which of the following is a sink for CO ? Answer: 1. Micro organisms present in the soil Key idea: CO is removed from air mainly by soil micro-organisms. Certain soil bacteria and fu... 1
- The element Z = 114 has been discovered recently. It will belong to which of the following family/group and electronic configuration ? Answer: 1. Carbon family, [Rn] 5f¹⁴6d¹⁰7s²7p² Key idea: element 114 lies in the same group as Pb (Z = 82), one period lower, so its outer sh... 1