Chemistry
- 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... 1
- 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... 1
- 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=... 1
- 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... 1
- 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... 1
- 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... 1
- 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... 1
- 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... 1
- 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... 1
- 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... 1
- 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... 1