NEET UG

2,056 solved questions 5 notes 85 tests

Ask a question

Which one of the following orders is correct for the bond dissociation enthalpy of halogen molecules ? Answer: 2. Cl₂ > Br₂ > F₂ > I₂ Key idea: bond dissociation enthalpy generally falls down group 17 (bigger atoms, longer bonds), but F₂ is un... General trends, Group 17 and 18 1 answer
Fog is a colloidal solution of : Answer: 1. Liquid in gas Key idea: fog consists of tiny water droplets (liquid) dispersed in air (gas), so it is a colloid of liquid in gas,... Lyophilic and lyophobic sols 1 answer
The pressure of H_2 required to make the potential of H_2 - electrode zero in pure water at 298 K is : Answer: 1. 10⁻¹⁴ atm Key idea: for the half cell 2H^++2e^-→ H₂ , the Nernst equation is E=0-0.059/2logfracP_(H_2)[H^+]² In pure water [H^+]=... EMF, Nernst equation and applications 1 answer
Which of the following statements about the composition of the vapour over an ideal 1 : 1 molar mixture of benzene and toluene is correct ? Assume that the temperature is constant at 25°C. (Given, Vapour Pressure Data at 25°C, benzene = 12.8 kPa, tol… Answer: 1. The vapour will contain a higher percentage of benzene. Key idea: the component with the higher vapour pressure is more volatile... Vapour pressure and Raoult's law 1 answer
Lithium has a bcc structure. Its density is 530\ kg\ m^-3 and its atomic mass is 6.94\ g\ mol^-1. Calculate the edge length of a unit cell of Lithium metal. (N_A = 6.02×10^23\ mol^-1) Answer: 2. 352 pm Key idea: ρ=Z M/N_A a³ , with Z = 2 for bcc. ρ=530\ mathrmkg m⁻³=0.530\ mathrmg cm⁻³ . a³=frac2×6.946.02×10²³×0.530=4.35×1... Atomic and molecular masses, mole concept, molar mass 1 answer
Equal moles of hydrogen and oxygen gases are placed in a container with a pin-hole through which both can escape. What fraction of the oxygen escapes in the time required for one-half of the hydrogen to escape ? Answer: 1. 1/8 Key idea: Graham's law, rate of effusion ∝ 1/√(M) . fracr_(H_2)r_(O_2)=√(32/2)=4 Both gases start with equal moles and leave... Atomic and molecular masses, mole concept, molar mass 1 answer
Natural rubber has : Answer: 1. All cis-configuration Key idea: natural rubber is cis-1,4-polyisoprene. All the double bonds in the chain have cis configuration,... Functional groups, homologous series, classification 1 answer
Which of the following is an analgesic ? Answer: 1. Novalgin Key idea: an analgesic relieves pain. Novalgin is an analgesic (and antipyretic). Penicillin, streptomycin and chloromyc... Functional groups, homologous series, classification 1 answer
In a protein molecule various amino acids are linked together by : Answer: 3. peptide bond Key idea: amino acids join through the amide linkage between the -COOH of one and the -NH₂ of the next, formed by lo... Amino acids, peptide bond, protein structure, denaturation 1 answer
Consider the molecules CH_4, NH_3 and H_2O. Which of the given statements is false ? Answer: 2. The H-O-H bond angle in H₂O is larger than the H-C-H bond angle in CH₄ . Key idea: lone pairs repel more than bond pairs, so bond... VSEPR theory and shapes of molecules 1 answer
The rate of a first-order reaction is 0.04\ mol\ l^-1\ s^-1 at 10 seconds and 0.03\ mol\ l^-1\ s^-1 at 20 seconds after initiation of the reaction. The half-life period of the reaction is : Answer: 1. 24.1 s Key idea: for a first-order reaction, rate = k[A] , so the ratio of rates equals the ratio of concentrations. [A]₁₀/[A]₂₀=... Integrated rate equations and half-life (zero and first order) 1 answer
In which of the following options the order of arrangement does not agree with the variation of property indicated against it ? Answer: 3. I < Br < Cl < F (increasing electron gain enthalpy) Key idea: compare each series with the real trend. Option 1: isoelectronic io... Ionization enthalpy and electron gain enthalpy 1 answer
Which of the following statements is false ? Answer: 3. Ca²⁺ ions are not important in maintaining the regular beating of the heart. Key idea: mathrmCa²⁺ and mathrmMg²⁺ both have import... Modern periodic law and periodic table, s, p, d, f blocks 1 answer
Which of the following statements about hydrogen is incorrect ? Answer: 1. Hydrogen has three isotopes of which tritium is the most common. Key idea: check each statement against NCERT facts and pick the... Modern periodic law and periodic table, s, p, d, f blocks 1 answer
MY and NY_3, two nearly insoluble salts, have the same K_sp values of 6.2×10^-13 at room temperature. Which statement would be true in regard to MY and NY_3 ? Answer: 2. The molar solubility of MY in water is less than that of NY₃ . Key idea: compare solubilities from the K_sp expression for each s... Solubility product 1 answer
In the reaction H-C CH [(2)\ CH_3CH_2Br](1)\ NaNH_2/liq.NH_3 X [(2)\ CH_3CH_2Br](1)\ NaNH_2/liq.NH_3 Y, X and Y are : Answer: 1. X = 1-Butyne ; Y = 3-Hexyne Key idea: the terminal alkyne H is acidic, so NaNH₂ removes it and the acetylide ion attacks the alky... Alkynes: acidic character and addition reactions 1 answer
The correct statement regarding a carbonyl compound with a hydrogen atom on its alpha-carbon, is : Answer: 4. a carbonyl compound with a hydrogen atom on its alpha-carbon rapidly equilibrates with its corresponding enol and this process is... Alpha-hydrogen acidity, aldol, Cannizzaro, haloform 1 answer
Among the following, the correct order of acidity is : Answer: 2. HClO < HClO₂ < HClO₃ < HClO₄ Key idea: in oxoacids of the same halogen, acidity rises with the number of oxygen atoms (higher oxi... General trends, Group 17 and 18 1 answer
Which one of the following characteristics is associated with adsorption ? Answer: 2. Δ G , Δ H and Δ S all are negative Key idea: adsorption is spontaneous, exothermic and reduces the freedom of the adsorbate. Spon... Lyophilic and lyophobic sols 1 answer
Given the value of Rydberg constant is 10^7\ m^-1, the wave number of the last line of the Balmer series in hydrogen spectrum will be : Answer: 3. 0.25×10⁷\ m⁻¹ Key idea: barν=R(dfrac12²-dfrac1n²) ; the last Balmer line has n→∞ . barν=R/4=10⁷/4=0.25×10⁷\ m⁻¹ . Bohr model, energy levels, hydrogen spectrum 1 answer
A potentiometer wire is 100 cm long and a constant potential difference is maintained across it. Two cells are connected in series first to support one another and then in opposite direction. The balance points are obtained at 50 cm and 10 cm from th… Answer: 4. 3 : 2 Key idea: balance length is proportional to the emf in the circuit. Supporting: ε₁+ε₂∝50 ; opposing: ε₁-ε₂∝10 . So ε₁∝30 an... Internal resistance, emf, cells in series and parallel 1 answer
When a metallic surface is illuminated with radiation of wavelength λ, the stopping potential is V. If the same surface is illuminated with radiation of wavelength 2λ, the stopping potential is V/4. The threshold wavelength for the metallic surface i… Answer: 4. 3λ Key idea: eV=hc/λ-hc/λ₀ . eV=hc/λ-φ and eV/4=hc/2λ-φ . Subtracting: 3/4eV=hc/2λ⇒ eV=2hc/3λ . φ=hc/λ-2hc/3λ=hc/3λ , so λ₀=3λ . Einstein's photoelectric equation, particle nature of light 1 answer
A small signal voltage V(t) = V_0 ω t is applied across an ideal capacitor C : Answer: 2. Over a full cycle the capacitor C does not consume any energy from the voltage source. Key idea: in an ideal capacitor, current l... Reactance, impedance, LCR series circuit, resonance 1 answer
An inductor 20 mH, a capacitor 50 μF and a resistor 40 Ω are connected in series across a source of emf V = 10 340 t. The power loss in A.C. circuit is : Answer: 1. 0.51 W Key idea: average power P=I_rms²R , with I_rms=V_rms/Z . X_L=ω L=340×0.02=6.8\ Ω ; X_C=dfrac1ω C≈58.8\ Ω . Z=√(40²+52²)=√(... Reactance, impedance, LCR series circuit, resonance 1 answer

← Previous

Page 84 of 86