The answer is van der Waal force, or to be precise, London dispersion forces.
This type of force is present between all molecules and they are caused by electrons that are orbiting the atom cores. The moving of the electrons can result in making the atom temporary dipole due to the asymmetry of electron distribution around the core. This temporary dipole now can interact with other atoms leading to an electrostatic interaction. The more electrons an atom has, the stronger are these intermolecular forces.
The 3% mass/volume H₂O₂ means 3 g of H₂O₂ in 100 ml of water.
Now, Molarity (M) = No. of moles of H₂O₂ / Volume of solution in liter
No. of moles of H₂O₂ = Mass / Molar mass = 3 g / 34 g/mol = 0.088 mol
So, molarity = 0.088 × 1000 ml / 100 ml = 0.88 M
In case of 2.25 % H₂O₂,
No of moles = 2.25 g / 34 g/mol = 0.066 mol
Molarity = 0.066 mol / 0.100 L = 0.66 M.
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