NEET UG
- The conductivity of centimolar solution of KCl at 25°C is 0.0210 ohm^-1 cm^-1 and the resistance of the cell containing the solution at 25°C is 60 ohm. The value of cell constant is - Answer: 4. 1.26 cm ⁻¹ Key idea: Cell constant = kappa × R . G^* = 0.0210\ Ω⁻¹mathrmcm⁻¹ × 60\ Ω = 1.26\ mathrmcm⁻¹ . Option 4. 1
- Which amongst the following options is correct graphical representation of Boyle's Law?(1) P vs T, straight lines through origin labelled V_1, V_2, V_3 with V_1<V_2<V_3; (2) P vs V, hyperbolas labelled T_1, T_2, T_3 with T_3>T_2>T_1; (3) P vs 1/V, st… Answer: 3. P vs 1/V lines, T ₃ >T ₂ >T ₁ (graph) Key idea: Boyle's law: at constant T, P ∝ 1/V , so P plotted against 1/V is a straight line... 1
- Given below are two statements :Statement I : A unit formed by the attachment of a base to 1' position of sugar is known as nucleosideStatement II : When nucleoside is linked to phosphorous acid at 5'-position of sugar moiety, we get nucleotide.In th… Answer: 4. Statement I is true but Statement II is false. Key idea: Nucleoside = base + sugar; nucleotide = nucleoside + phosphoric acid. St... 1
- A compound is formed by two elements A and B. The element B forms cubic close packed structure and atoms of A occupy 1/3 of tetrahedral voids. If the formula of the compound is A_xB_y, then the value of x + y is in option Answer: 2. 5 Key idea: In ccp, if B atoms number N, there are N octahedral and 2N tetrahedral voids. Take 1 unit cell: B = 4 atoms; tetrahed... 1
- The correct order of energies of molecular orbitals of N_2 molecule, is : Answer: 2. σ 1s<σ^* 1s<σ 2s<σ^* 2s<(π 2p_x=π 2p_y)<σ 2p_z<(π^* 2p_x=π^* 2p_y)<σ^* 2p_z Key idea: For molecules with 14 or fewer electrons (... 1
- Given below are two statements : one is labelled as Assertion A and the other is labelled as Reason R :Assertion A : A reaction can have zero activation energy.Reasons R : The minimum extra amount of energy absorbed by reactant molecules so that thei… Answer: 1. A is false but R is true. Key idea: Activation energy is the extra energy reactants must absorb to reach the threshold energy: E_... 1
- For a certain reaction, the rate = k[A]^2[B], when the initial concentration of A is tripled keeping concentration of B constant, the initial rate would Answer: 4. increase by a factor of nine. Key idea: Rate is proportional to [A]² when B is constant. New rate = k(3[A])²[B] = 9k[A]²[B] , so... 1
- Which one is an example of heterogenous catalysis? Answer: 1. Combination between dinitrogen and dihydrogen to form ammonia in the presence of finely divided iron. Key idea: In heterogeneous... 1
- The element expected to form largest ion to achieve the nearest noble gas configuration is : Answer: 4. N Key idea: For isoelectronic ions (all 10 electrons), the one with the lowest nuclear charge is the largest. The ions are Na^+ (... 1
- Which one of the following statements is correct? Answer: 2. The daily requirement of Mg and Ca in the human body is estimated to be 0.2 - 0.3 g. Key idea: Recall the biological roles of Mg... 1
- Which of the following statements are NOT correct?A. Hydrogen is used to reduce heavy metal oxides to metals.B. Heavy water is used to study reaction mechanism.C. Hydrogen is used to make saturated fats from oils.D. The H-H bond dissociation enthalpy… Answer: 4. D, E only Key idea: Check each statement. A. True: H₂ reduces oxides of less active (heavy) metals. B. True: D₂O is used as a tra... 1
- The stability of Cu^2+ is more than Cu^+ salts in aqueous solution due to - Answer: 4. hydration energy. Key idea: Stability in aqueous solution depends on the overall enthalpy change, where hydration enthalpy often... 1
- Given below are two statements : one is labelled as Assertion A and the other is labelled as Reason R :Assertion A : Helium is used to dilute oxygen in diving apparatus.Reasons R : Helium has high solubility in O_2.In the light of the above statement… Answer: 4. A is true but R is false. Key idea: Gases dissolve in blood at high pressure; helium is chosen because it is hardly soluble. Asse... 1
- Weight (g) of two moles of the organic compound, which is obtained by heating sodium ethanoate with sodium hydroxide in presence of calcium oxide is : Answer: 3. 32 Key idea: Sodium ethanoate heated with soda lime (NaOH + CaO) undergoes decarboxylation to give an alkane with one carbon fewe... 1
- The given compoundC_6H_5-CH=CH-CH(X)-CH_2CH_3 (benzene ring attached to CH=CH-CH(X)-CH_2CH_3)is an example of ________. Answer: 4. allylic halide Key idea: A halide is named by the carbon that carries the halogen. In C₆H₅-CH=CH-CH(X)-CH₂CH₃ , X is on an sp³ ca... 1
- Some tranquilizers are listed below. Which one from the following belongs to barbiturates? Answer: 1. Veronal Key idea: Barbiturates are derivatives of barbituric acid. Veronal (barbital) is a barbiturate (others: luminal, seconal)... 1
- Identify the product in the following reaction :Benzenediazonium chloride (C_6H_5N_2^+Cl^-) with (i) Cu_2Br_2/HBr (ii) Mg/dry ether (iii) H_2O → Product Answer: 3. benzene (structure) Key idea: Follow each step: Sandmeyer reaction, then Grignard formation, then hydrolysis. C₆H₅N₂^+Cl^- with C... 1
- Complete the following reaction :cyclohexanone [A] HCN cyclohexanone cyanohydrin (1-hydroxycyclohexanecarbonitrile) [B] [Δ]conc.\ H_2SO_4 [C][C] is ________. Answer: 1. cyclohex-1-ene-1-carboxylic acid (structure) Key idea: Conc. H₂SO₄ with heat does two things to a cyanohydrin: it hydrolyses -CN... 1
- Taking stability as the factor, which one of the following represents correct relationship? Answer: 1. TlI > TlI ₃ Key idea: In group 13 the +1 state becomes more stable down the group because of the inert pair effect; for Tl, +1 is... 1
- Match List - I with List - II :List - I: A. Coke B. Diamond C. Fullerene D. GraphiteList - II: I. Carbon atoms are sp^3 hybridised. II. Used as a dry lubricant III. Used as a reducing agent IV. Cage like moleculesChoose the correct answer from the op… Answer: 4. A-III, B-I, C-IV, D-II Key idea: Match each form of carbon with its structure or use. A. Coke is used as a reducing agent in meta... 1
- In Lassaigne's extract of an organic compound, both nitrogen and sulphur are present, which gives blood red colour with Fe^3+ due to the formation of - Answer: 1. [Fe(SCN)]²⁺ Key idea: When N and S are both present, Na fusion forms sodium thiocyanate, NaSCN, in the Lassaigne's extract. Na +... 1
- The right option for the mass of CO_2 produced by heating 20 g of 20% pure limestone is (Atomic mass of Ca = 40)CaCO_3 1200\ K CaO + CO_2 Answer: 3. 1.76 g Key idea: Only the pure CaCO₃ decomposes; find its moles and use 1:1 mole ratio with CO₂ . Pure CaCO₃ = 20 × 20/100 = 4 g.... 1
- An electric dipole is placed as shown in the figure. The electric potential (in 10^2 V) at point P due to the dipole is (ε_0 = permittivity of free space and 1/4πε_0=K): Answer: 2. (3/8)qK P lies on the axis of the dipole. Distances from P: to +q it is 5-3=2 cm, to -q it is 5+3=8 cm. V=Kq(dfrac10.02-dfrac10.0... 1
- A bullet from a gun is fired on a rectangular wooden block with velocity u. When bullet travels 24 cm through the block along its length horizontally, velocity of bullet becomes u/3. Then it further penetrates into the block in the same direction bef… Answer: 2. 27 cm Assume a constant resistive force, so deceleration a is constant. Use v²=u²-2as . First 24 cm: (u/3)²=u²-2a(24)⇒ 48a=8u²/9⇒... 1