Chemistry Q51 – JEE-MAIN 2026

Home Chemistry Basic ChemistryQuestion #40

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:

Clue 1 of 3: Moles and Avogadro's Number

The total number of atoms in a substance is determined by the number of moles of the substance, the number of atoms per molecule, and Avogadro's number ( $N_{A}$ ).

🧠 Full Solution Path

Step 1: Calculate total atoms for each substance✦ Active

We need to calculate the total number of atoms for each given case. Let $N_{A}$ be Avogadro's number ( $6.022 \times 10^{23}$ ). The number of atoms is given by: $Moles of substance \times Atoms per molecule \times N_{A}$ .

(A) 2 moles of cyclohexane (C_{6} H_{12}) :

Moles of C_{6} H_{12} = 2 mol

Atoms per molecule = 6 (C) + 12 (H) = 18 atoms/molecule

Total atoms (A) = 2 \times 18 \times N_{A} = 36 N_{A} atoms

(B) 684 g of sucrose (C_{12} H_{22} O_{11}) :

Molar mass of C_{12} H_{22} O_{11} = (12 \times 12) + (22 \times 1) + (11 \times 16) = 144 + 22 + 176 = 342 g/mol

Moles of sucrose = \frac{684 g}{342 g/mol} = 2 mol

Atoms per molecule = 12 (C) + 22 (H) + 11 (O) = 45 atoms/molecule

Total atoms (B) = 2 \times 45 \times N_{A} = 90 N_{A} atoms

(C) 90.8 L of dihydrogen (H_{2}) at STP:

Moles of H_{2} = \frac{90.8 L}{22.4 L/mol} \approx 4.0536 mol

Atoms per molecule = 2 atoms/molecule

Total atoms (C) = 4.0536 \times 2 \times N_{A} \approx 8.107 N_{A} atoms

Step 2: Compare the number of atoms○ Expand

Now, we compare the calculated total number of atoms for each case:

(A) 36 N_{A}

(B) 90 N_{A}

(C) 8.107 N_{A}

Arranging these values in decreasing order: $90 N_{A} > 36 N_{A} > 8.107 N_{A}$ .

Step 3: Determine the correct order○ Expand

Based on the comparison, the correct order of the total number of atoms is $B > A > C$ .

💡 Teacher's Secret Hint

Ensure to use the correct molar mass and molar volume at STP for accurate calculations.

✦ STEM Console utilizes AI models to generate step-by-step explanations and math clues. AI can make mistakes.

Chemistry Question 51 – JEE-MAIN 2026

Clue 1 of 3: Moles and Avogadro's Number

🧠 Full Solution Path