WBJEE 2025 Physics and Chemistry Papers

Let's break down the problem step-by-step:
Determine the Moles of Water
The molar mass of water (H2O) is approximately:
MH2O=2(1)+16=18g∕mol
For 0.36 g of water, the number of moles is:
Calculate the Number of Water Molecules
Using Avogadro's number ( NA≈6.02×1023 molecules/mol), the total number of water molecules is:
Number of molecules =0.02‌mol×6.02×1023 molecules ∕mol=1.204×1022 molecules
Find the Number of Oxygen Atoms
Each water molecule has one oxygen atom. Therefore, the number of oxygen atoms equals the number of water molecules:
Oxygen atoms =1.204×1022
Thus, the number of oxygen atoms present is:
1.205×1022
This matches Option B.