#neet
- Reaction between benzaldehyde and acetophenone in presence of dilute NaOH is known as : Answer: 4. Cross Aldol condensation Benzaldehyde has no α -hydrogen, while acetophenone has α -hydrogens. In dilute NaOH, acetophenone forms... 1
- Paper chromatography is an example of : Answer: 2. Partition chromatography In paper chromatography the stationary phase is water held in the cellulose fibres of the paper, and the... 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
- A mixture of N_2 and Ar gases in a cylinder contains 7 g of N_2 and 8 g of Ar. If the total pressure of the mixture of the gases in the cylinder is 27 bar, the partial pressure of N_2 is :[Use atomic masses (in g mol^-1) : N = 14, Ar = 40] Answer: 3. 15 bar Partial pressure p_i=x_i P_total . Moles N₂=7/14=0.25 ; moles Ar =8/40=0.2 . x_(N_2)=0.25/0.45=5/9 . p_(N_2)=5/9×27=15 bar... 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
- A tertiary butyl carbocation is more stable than a secondary butyl carbocation because of which of the following ? Answer: 4. Hyperconjugation Methyl groups attached to the positive carbon stabilise it by hyperconjugation: C-H sigma electrons delocalise i... 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
- Elimination reaction of 2-Bromo-pentane to form pent-2-ene is :(a) β-Elimination reaction(b) Follows Zaitsev rule(c) Dehydrohalogenation reaction(d) Dehydration reaction Answer: 1. (a), (b), (c) 2-Bromopentane CH₃CHBrCH₂CH₂CH₃ loses HBr with alcoholic KOH. (a) H is removed from the carbon beta to the carbon b... 1
- The mixture which shows positive deviation from Raoult's law is : Answer: 1. Ethanol + Acetone Positive deviation occurs when A-B attractions are weaker than A-A and B-B. Ethanol has strong hydrogen bonding... 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
- 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 not correct about carbon monoxide ? Answer: 3. The carboxyhaemoglobin (haemoglobin bound to CO) is less stable than oxyhaemoglobin. CO binds to haemoglobin to form carboxyhaemo... 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
- 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 one of the followings has maximum number of atoms ? Answer: 4. 1 g of Li(s) [Atomic mass of Li = 7] Number of atoms is proportional to moles of atoms = mass / atomic mass (all masses are 1 g).... 1
- The number of protons, neutrons and electrons in ^175_71Lu, respectively, are : Answer: 1. 71, 104 and 71 For ^A_ZX : protons =Z=71 ; neutrons =A-Z=175-71=104 ; electrons (neutral atom) =71 . Answer: 71, 104 and 71, opti... 1
- What is the change in oxidation number of carbon in the following reaction ?CH_4(g) + 4Cl_2(g) → CCl_4(l) + 4HCl(g) Answer: 3. - 4 to +4 Find carbon's oxidation number on each side. In CH₄ : x+4(+1)=0 , so x=-4 . In CCl₄ : x+4(-1)=0 , so x=+4 . The change... 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
- 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
- Measuring Zeta potential is useful in determining which property of colloidal solution ? Answer: 3. Stability of the colloidal particles Zeta potential is the potential difference between the fixed layer of charge on a colloidal... 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
- Match the following and identify the correct option.(a) CO(g) + H_2(g) (i) Mg(HCO_3)_2 + Ca(HCO_3)_2(b) Temporary hardness of water (ii) An electron deficient hydride(c) B_2H_6 (iii) Synthesis gas(d) H_2O_2 (iv) Non-planar structure Answer: 1. (a)-(iii), (b)-(i), (c)-(ii), (d)-(iv) (a) CO+H₂ is water gas, called synthesis gas: (iii). (b) Temporary hardness is due to Mg(H... 1
- The QRS complex in a standard ECG represents : Answer: 3. Depolarisation of ventricles In an ECG, the P wave is atrial depolarisation, the QRS complex is ventricular depolarisation (the s... 1
- Which of the following statements is correct ? Answer: 1. Adenine pairs with thymine through two H-bonds. In DNA, adenine pairs with thymine by two hydrogen bonds, and guanine pairs with... 1