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Some Basic Concepts of Chemistry

JEE Main 2025 (Online) 3rd April Morning ShiftMCQEasy📈 Topic in 14% papers+4−1
Ques. 1JEE Main 2025, 3 April (Morning Shift)

Among 10-9 g (each) of the following elements, which one will have the highest number of atoms? Element: Pb, Po, Pr and Pt

  1. Pr
  2. Pt
  3. Po
  4. Pb

Answer

(1) Pr

Solution

Number of atoms = mM NA

For the same mass m, the element with the smallest molar mass M has the most atoms.

Molar masses ( g mol-1): Pr (Z = 59) = 140.9; Pt (Z = 78) = 195.1; Pb (Z = 82) = 207.2; Po (Z = 84) = 209

Pr (praseodymium) has the highest number of atoms.

Answer: (1)

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Ques. 2JEE Main 2025, 3 April (Evening Shift)

Mass of magnesium required to produce 220 mL of hydrogen gas at STP on reaction with excess of dil. HCl is Given: Molar mass of Mg is 24 g mol-1.

  1. 0.24 mg
  2. 235.7 g
  3. 2.444 g
  4. 236 mg
Ques. 3JEE Main 2025, 3 April (Evening Shift)

10 mL of 2 M NaOH solution is added to 20 mL of 1 M HCl solution kept in a beaker. Now, 10 mL of this mixture is poured into a volumetric flask of 100 mL containing 2 moles of HCl and made the volume up to the mark with distilled water. The solution in this flask is :

  1. 0.2 M NaCl solution
  2. 20 M HCl solution
  3. Neutral solution
  4. 10 M HCl solution
Ques. 4JEE Main 2025, 3 April (Evening Shift)

X g of nitrobenzene on nitration gave 4.2 g of m-dinitrobenzene. X = g. (nearest integer) [Given : molar mass (in g mol-1) C : 12, H : 1, O : 16, N : 14]

Ques. 5JEE Main 2025, 2 April (Morning Shift)

CaCO3(s)+2HCl(aq) CaCl2(aq)+CO2(g)+H2O(l) Consider the above reaction, what mass of CaCl2 will be formed if 250 mL of 0.76 M HCl reacts with 1000 g of CaCO3 ? (Given : Molar mass of Ca, C, O, H and Cl are 40, 12, 16, 1 and 35.5 g mol-1, respectively)

  1. 3.908 g
  2. 2.636 g
  3. 10.545 g
  4. 5.272 g
Ques. 6JEE Main 2025, 2 April (Morning Shift)

On complete combustion 1.0 g of an organic compound (X) gave 1.46 g of CO2 and 0.567 g of H2O. The empirical formula mass of compound (X) is g. (Given molar mass in g mol-1 C : 12, H : 1, O : 16)

  1. 60
  2. 45
  3. 30
  4. 15
Ques. 7JEE Main 2025, 2 April (Morning Shift)

0.1 mol of the following given antiviral compound (P) will weigh 10-1 g (nearest integer). [figure] (Given : molar mass in g mol-1 H : 1, C : 12, N : 14, O : 16, F : 19, I : 127)

Ques. 8JEE Main 2025, 2 April (Evening Shift)

'x' g of NaCl is added to water in a beaker with a lid. The temperature of the system is raised from 1 C to 25 C. Which out of the following plots, is best suited for the change in the molarity (M) of the solution with respect to temperature? [Consider the solubility of NaCl remains unchanged over the temperature range]

  1. [figure]
  2. [figure]
  3. [figure]
  4. [figure]
Ques. 9JEE Main 2025, 29 January (Morning Shift)

Choose the correct statements. Choose the correct answer from the options given below :

  1. (B), (C) and (D) Only
  2. (A), (B) and (C) Only
  3. (C), (D) and (E) Only
  4. (A), (D) and (E) Only
Ques. 10JEE Main 2025, 29 January (Evening Shift)

0.1 M solution of KI reacts with excess of H2SO4 and KIO3 solutions. According to equation 5I- + IO3- + 6H+ 3I2 + 3H2O Identify the correct statements : Choose the correct answer from the options given below :

  1. (C) and (D) only
  2. (A) and (B) only
  3. (B) and (C) only
  4. (A) and (D) only
Ques. 11JEE Main 2025, 28 January (Morning Shift)

The molarity of a 70\% (mass/mass) aqueous solution of a monobasic acid (X) is 10-1 M (Nearest integer) [Given: Density of aqueous solution of (X) is 1.25 g mL-1 Molar mass of the acid is 70 g mol-1]

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