Q.Write the formula to calculate % atom economy.

Atom economy = (product mass/total reactant mass)×100. Nanomaterials used in targeted drug delivery and water purification.

Atom economy: a quantitative measure, used in green chemistry, of how much of the mass of the starting materials ends up incorporated into the desired product rather than being wasted as by-products:

$\text{Atom economy} = \dfrac{\text{molar mass of desired product}}{\text{sum of molar masses of all reactants}} \times 100\%$

A reaction with high atom economy is more efficient and environmentally friendly, minimising waste.

Applications of nanomaterials (any two):

1. Medicine: nanoparticles are used as carriers for targeted drug delivery, delivering medication precisely to diseased cells/tissues, reducing side effects.

2. Water purification: metal/metal-oxide nanoparticles (e.g. silver, titanium dioxide) are used in filters to remove bacteria, heavy metals, and organic pollutants from water.

   (Other valid examples: electronics/nanotransistors, sunscreens with ZnO/TiO$_2$ nanoparticles, catalysis.)