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Some Basic Concepts of Chemistry · Question 3

JEE Main 2026 (Online) 6th April Evening ShiftMCQEasy📈 Topic in 19% papers+4−1
1

Which of the following contain the same number of atoms? (Given : Molar mass in g mol-1 of H, He, O and S are 1, 4, 16 and 32 respectively) Choose the correct answer from the options given below :

  1. A and B only
  2. B and C only
  3. C and D only
  4. A, C and E only

Answer

(4) A, C and E only

Solution

Number of atoms ∝ moles of atoms = moles of molecules × atomicity

A. 2 g O2: n = 232 = 0.0625 mol ⇒ atoms = 0.0625 × 2 = 0.125 mol

B. 4 g SO2: n = 464 = 0.0625 mol ⇒ atoms = 0.0625 × 3 = 0.1875 mol

C. 1400 mL O2 at STP: n = 1.422.4 = 0.0625 mol ⇒ atoms = 0.0625 × 2 = 0.125 mol

D. 0.05 L He at STP: n = 0.0522.4 = 2.23 10-3 mol (monoatomic) ⇒ atoms = 2.23 10-3 mol

E. 0.0625 mol H2 ⇒ atoms = 0.0625 × 2 = 0.125 mol

∴ A, C and E contain the same number of atoms (0.125 NA each).

Answer: (4)

JEE Main 2026 (Online) 6th April Evening Shift

Keep practising — Some Basic Concepts of Chemistry

2

How many grams of residue is obtained by heating 2.76 g of silver carbonate? (Given : Molar mass of C, O and Ag are 12, 16 and 108 g mol-1 respectively)

  1. 1.08 g
  2. 2.16 g
  3. 3.24 g
  4. 4.32 g
JEE Main 2026 (Online) 5th April Morning Shift
3

What volume of hydrogen gas at STP would be liberated by action of 50 mL of H2SO4 of 50% purity (density = 1.3 g mL-1) on 20 g of zinc? Given : Molar mass of H, O, S, Zn are 1, 16, 32, 65 g mol-1 respectively.

  1. 5.824 L
  2. 7.428 L
  3. 6.892 L
  4. 8.375 L
JEE Main 2026 (Online) 5th April Evening Shift
4

Number of moles and number of molecules in 1.4187 L of SO2 at STP respectively are

  1. 0.1266; 3.812 1022
  2. 0.0633; 3.812 1022
  3. 0.1266; 7.6238 1022
  4. 0.0633; 7.6238 1022
JEE Main 2026 (Online) 4th April Morning Shift
5

The correct order of total number of atoms present in (A) 2 moles of cyclohexane (B) 684 g of sucrose (C) 90.8 L of dihydrogen at STP is :

  1. C > A > B
  2. C > B > A
  3. B > C > A
  4. B > A > C
JEE Main 2026 (Online) 4th April Evening Shift
6

The mass of iron converted into Fe3O4 by the action of 18 g of steam is : (Given : Molar mass of H, O and Fe are 1, 16 and 56 g mol-1 respectively) Assume iron is present in excess :

  1. 2.1 g
  2. 4.2 g
  3. 21 g
  4. 42 g
JEE Main 2026 (Online) 2nd April Morning Shift
7

The ratio of mass percentage (w/w) of C : H in a hydrocarbon is 12 : 1. It has two carbon atoms. The weight (in g) of CO2(g) formed when 3.38 g of this hydrocarbon is completely burnt in oxygen is : (Given : Molar mass in g mol-1 C : 12, H : 1, O : 16)

  1. 5.68
  2. 11.44
  3. 22.74
  4. 17.05
JEE Main 2026 (Online) 2nd April Evening Shift
8

For the given reaction; CaCO3 + 2HCl CaCl2 + H2O + CO2 If 90 g CaCO3 is added to 300 mL of HCl which contains 38.55% HCl by mass and has density 1.13 g mL-1, then which of the following option is correct? Given molar mass of H, Cl, Ca and O are 1, 35.5, 40 and 16 g mol-1 respectively.

  1. 64.97 g of HCl remains unreacted
  2. 60.32 g of HCl remains unreacted
  3. 32.85 g of CaCO3 remains unreacted
  4. 97.30 g of HCl reacted
JEE Main 2026 (Online) 28th January Evening Shift
9

A student has planned to prepare acetanilide from aniline using acetic anhydride. The student has started from 9.3 g of aniline. However, the student has managed to obtain 11 g of dry acetanilide. The % yield of this reaction is :-

  1. 59.5\%
  2. 72.5\%
  3. 97.5\%
  4. 81.5\%
JEE Main 2026 (Online) 24th January Evening Shift
10

x mg of pure HCl was used to make an aqueous solution. 25.0 mL of 0.1 M Ba(OH)2 solution is used when the HCl solution was titrated against it. The numerical value of x is 10-1. (Nearest integer) Given : Molar mass of HCl and Ba(OH)2 are 36.5 and 171.0 g mol-1 respectively.

JEE Main 2026 (Online) 23rd January Morning Shift
11

In the reaction, 2Al(s) + 6HCl(aq) 2Al3+(aq) + 6Cl-(aq) + 3H2(g)

  1. 12 L HCl(aq) is consumed for every 6 L H2(g) produced.
  2. 11.2 L H2(g) at STP is produced for every mole of HCl consumed.
  3. 33.6 L H2(g) is produced regardless of temperature and pressure for every mole of Al that reacts.
  4. 67.2 L H2(g) at STP is produced for every mole of Al that reacts.
JEE Main 2026 (Online) 22nd January Morning Shift

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