Chemistry
- Which of the following is correct with respect to -I effect of the substituents ? (R = alkyl) Answer: 3. - NR ₂ < - OR < - F The -I effect increases with the electronegativity of the atom attached to the carbon chain: N < O < F. Since... 1
- Regarding cross-linked or network polymers, which of the following statements is incorrect ? Answer: 4. They contain strong covalent bonds in their polymer chains. Cross-linked (network) polymers are formed from bi- and tri-functiona... 1
- The difference between amylose and amylopectin is Answer: 1. Amylopectin have 1 → 4 α -linkage and 1 → 6 α -linkage Both amylose and amylopectin are polymers of α -D-glucose, and they differ... 1
- In the structure of ClF_3, the number of lone pairs of electrons on central atom 'Cl' is Answer: 3. two Count electron pairs on Cl in ClF₃ : Cl has 7 valence electrons, 3 are used for bonds with F, leaving 4 electrons = 2 lone pa... 1
- Considering Ellingham diagram, which of the following metals can be used to reduce alumina ? Answer: 2. Mg In an Ellingham diagram, a metal can reduce an oxide only if its own oxide-formation line lies below that of the oxide to be r... 1
- The correct order of atomic radii in group 13 elements is Answer: 4. B < Ga < Al < In < Tl Atomic radius generally increases down a group, but Ga is smaller than Al. Gallium follows the d-block (3d)... 1
- Which of the following oxides is most acidic in nature ? Answer: 3. BeO Acidic character of oxides falls as the metallic character of the element rises. In group 2, MgO, CaO and BaO are basic (basi... 1
- Given van der Waals constant for NH_3, H_2, O_2 and CO_2 are respectively 4.17, 0.244, 1.36 and 3.59, which one of the following gases is most easily liquefied ? Answer: 1. NH ₃ The more easily a gas liquefies, the stronger its intermolecular attraction, and the van der Waals constant a measures exact... 1
- Following solutions were prepared by mixing different volumes of NaOH and HCl of different concentrations :a. 60 mL M/10 HCl + 40 mL M/10 NaOHb. 55 mL M/10 HCl + 45 mL M/10 NaOHc. 75 mL M/5 HCl + 25 mL M/5 NaOHd. 100 mL M/10 HCl + 100 mL M/10 NaOHpH… Answer: 4. c pH = 1 means [H^+]=0.1 M, so excess strong acid of that concentration must remain after mixing. a: HCl 6 mmol, NaOH 4 mmol, exc... 1
- The solubility of BaSO_4 in water is 2.42×10^-3 gL^-1 at 298 K. The value of its solubility product (K_sp) will be(Given molar mass of BaSO_4 = 233 g mol^-1) Answer: 1. 1.08×10⁻¹⁰ mol ² L ⁻² Convert solubility to mol/L, then use K_sp=s² for a 1:1 salt. s=dfrac2.42×10⁻³233=1.04×10⁻⁵\ mathrmmol L⁻¹... 1
- Nitration of aniline in strong acidic medium also gives m-nitroaniline because Answer: 4. In acidic (strong) medium aniline is present as anilinium ion. Aniline is nitrated with a mixture of HNO₃ and H₂SO₄ , which is st... 1
- Compound A, C_8H_10O, is found to react with NaOI (produced by reacting Y with NaOH) and yields a yellow precipitate with characteristic smell.A and Y are respectively Answer: 2. 1-phenylethanol (C ₆ H ₅ -CH(OH)-CH ₃ ) and I ₂ A positive iodoform test (yellow precipitate with characteristic smell) needs a C... 1
- A mixture of 2.3 g formic acid and 4.5 g oxalic acid is treated with conc. H_2SO_4. The evolved gaseous mixture is passed through KOH pellets. Weight (in g) of the remaining product at STP will be Answer: 2. 2.8 Conc. H₂SO₄ dehydrates both acids. KOH absorbs CO₂ , so only CO remains. HCOOH→ CO+H₂O : 2.3 g / 46 = 0.05 mol, gives 0.05 mo... 1
- Carboxylic acids have higher boiling points than aldehydes, ketones and even alcohols of comparable molecular mass. It is due to their Answer: 4. formation of intermolecular H-bonding Carboxylic acids form strong intermolecular hydrogen-bonded dimers, so more energy is neede... 1
- In the reaction[phenol + CHCl_3 + NaOH → sodium salicylaldehyde (o-O^-Na^+ C_6H_4 CHO), shown as a structure]the electrophile involved is Answer: 4. dichlorocarbene (:CCl ₂ ) This is the Reimer-Tiemann reaction. The electrophile is dichlorocarbene. The base removes a proton fro... 1
- Which one of the following elements is unable to form MF_6^3- ion ? Answer: 2. B mathrmMF₆³⁻ needs six F^- around M, so M must use d orbitals to exceed an octet. Boron is in period 2 and has no d orbitals; it... 1
- Which of the following statements is not true for halogens ? Answer: 2. All but fluorine show positive oxidation states. We need the statement that is NOT true for halogens. Option 1: Cl, Br, I and (as... 1
- On which of the following properties does the coagulating power of an ion depend ? Answer: 2. Both magnitude and sign of the charge on the ion According to the Hardy-Schulze rule, the ion that coagulates a colloid is the on... 1
- The correct order of N-compounds in its decreasing order of oxidation states is Answer: 1. HNO ₃ , NO, N ₂ , NH ₄ Cl Find the oxidation state of N in each compound. HNO₃ : +5 NO: +2 N₂ : 0 NH₄Cl : -3 The decreasing order... 1
- Which of the following molecules represents the order of hybridisation sp^2, sp^2, sp, sp from left to right atoms ? Answer: 3. CH ₂ =CH - C equiv CH A carbon in a double bond is sp² , one in a triple bond is sp . mathrmCH₂=CH-CequivCH has carbons sp²,sp²,s... 1
- Which of the following are not polymeric ? Answer: 3. Lipids Key idea: A polymer is a long chain of repeating monomer units. Proteins: chains of amino acids. Polysaccharides: chains o... 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 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
- 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