Chemistry
- Among the following alkaline earth metal halides, one which is covalent and soluble in organic solvents is : Answer: 4. Beryllium chloride Key idea: small, highly polarising mathrmBe²⁺ gives strong covalent character (Fajans' rules). BeCl₂ is covale... 1
- Noble gases are named because of their inertness towards reactivity. Identify an incorrect statement about them. Answer: 2. Noble gases have very high melting and boiling points. Key idea: noble gases are monoatomic and held only by very weak dispersion... 1
- The right option for the statement "Tyndall effect is exhibited by", is : Answer: 3. Starch solution Key idea: the Tyndall effect needs colloidal particles large enough (1 to 1000 nm) to scatter light. Starch forms... 1
- The compound which shows metamerism is : Answer: 4. C₄H₁₀O Key idea: metamerism occurs between compounds with the same functional group (usually ethers, ketones, secondary amines) b... 1
- Which one of the following polymers is prepared by addition polymerisation ? Answer: 1. Teflon Key idea: addition polymers form from unsaturated monomers by chain addition; condensation polymers lose small molecules.... 1
- The rate constant for a first order reaction is 4.606×10^-3 s^-1. The time required to reduce 2.0 g of the reactant to 0.2 g is : Answer: 3. 500 s For a first-order reaction t=2.303/klog[A]₀/[A] . t=frac2.3034.606×10⁻³log2.0/0.2=frac2.3034.606×10⁻³×1=500\ s Answer: opti... 1
- Match the following :Oxide | Nature(a) CO (i) Basic(b) BaO (ii) Neutral(c) Al_2O_3 (iii) Acidic(d) Cl_2O_7 (iv) AmphotericWhich of the following is correct option ? Answer: 2. (a)-(ii), (b)-(i), (c)-(iv), (d)-(iii) CO: neutral oxide (a)-(ii). BaO: basic oxide of an s-block metal (b)-(i). Al₂O₃ : amphoter... 1
- An alkene on ozonolysis gives methanal as one of the product. Its structure is : Answer: 3. Cyclohexyl-CH ₂ -CH=CH ₂ Ozonolysis cleaves C=C and gives a carbonyl on each carbon. Methanal (HCHO) comes only from a terminal =... 1
- Which of the following alkane cannot be made in good yield by Wurtz reaction ? Answer: 3. n-Heptane The Wurtz reaction ( 2RX+2Na→ R-R ) gives good yield only when both alkyl groups are the same, so one alkyl halide is u... 1
- Anisole on cleavage with HI gives : Answer: 1. Phenol (C ₆ H ₅ OH) + CH ₃ I Aryl alkyl ethers are cleaved by HI at the alkyl-oxygen bond. The ether oxygen is protonated, then I... 1
- Which of the following is a basic amino acid ? Answer: 4. Lysine A basic amino acid has an extra basic group (amino) in its side chain. Lysine, H₂N(CH₂)₄CH(NH₂)COOH , has two amino groups... 1
- Which of the following is a natural polymer ? Answer: 1. cis-1,4-polyisoprene Natural rubber is cis-1,4-polyisoprene, a polymer made by plants. Poly(butadiene-styrene) (SBR), polybutadie... 1
- Sucrose on hydrolysis gives : Answer: 3. α -D-Glucose + β -D-Fructose Sucrose is made of α -D-glucose and β -D-fructose joined through C1 of glucose and C2 of fructose (a... 1
- An increase in the concentration of the reactants of a reaction leads to change in : Answer: 4. collision frequency Raising reactant concentration puts more molecules in the same volume, so collisions per second (collision fr... 1
- The correct option for free expansion of an ideal gas under adiabatic condition is : Answer: 1. q = 0, Δ T = 0 and w = 0 Free expansion means expansion into vacuum, so external pressure is zero and work w=-P_extΔ V=0 . Adiaba... 1
- For the reaction, 2Cl(g) → Cl_2(g), the correct option is : Answer: 4. Δ_rH < 0 and Δ_rS < 0 2Cl(g)→ Cl₂(g) forms a Cl-Cl bond. Bond formation releases energy, so Δ_rH<0 . Two particles become one, so... 1
- The following metal ion activates many enzymes, participates in the oxidation of glucose to produce ATP and with Na, is responsible for the transmission of nerve signals. Answer: 4. Potassium Potassium ions activate many enzymes, take part in oxidation of glucose to give ATP, and together with sodium ions carr... 1
- Which of the following is the correct order of increasing field strength of ligands to form coordination compounds ? Answer: 1. SCN ^- < F ^- < C ₂ O ₄²⁻ < CN ^- From the spectrochemical series (weak to strong field): mathrmI^- So the increasing order is ma... 1
- Urea reacts with water to form A which will decompose to form B. B when passed through Cu^2+ (aq), deep blue colour solution C is formed. What is the formula of C from the following ? Answer: 2. [Cu(NH ₃ ) ₄ ] ²⁺ Urea + water: NH₂CONH₂+2H₂O→(NH₄)₂CO₃ (A). On decomposition: (NH₄)₂CO₃→ 2NH₃+CO₂+H₂O ; B is NH₃ . NH₃ with math... 1
- The calculated spin only magnetic moment of Cr^2+ ion is : Answer: 2. 4.90 BM Spin-only moment: μ=√(n(n+2)) BM, where n is the number of unpaired electrons. Cr (Z=24): 3d⁵4s¹ . mathrmCr²⁺ : 3d⁴ , so... 1
- Identify the correct statement from the following : Answer: 4. Pig iron can be moulded into a variety of shapes. Check each statement. (1) Wrought iron is the purest form of iron (about 0.2% c... 1
- Identify the incorrect statement. Answer: 4. The oxidation states of chromium in CrO ₄²⁻ and Cr ₂ O ₇²⁻ are not the same. Check each statement. (1) mathrmCr³⁺ (half-filled t_... 1
- HCl was passed through a solution of CaCl_2, MgCl_2 and NaCl. Which of the following compound(s) crystallise(s) ? Answer: 2. Only NaCl Passing HCl gas raises the Cl^- concentration. When the ionic product [Na^+][Cl^-] exceeds the solubility product of Na... 1
- Which of the following is a cationic detergent ? Answer: 3. Cetyltrimethyl ammonium bromide Cationic detergents have a positively charged head group, usually a quaternary ammonium salt. Cet... 1