Water is molecule formed by the covalent bonding of two atoms of hydrogen with one atom of oxygen. The chemical and physical properties of water are different from each of it's constituent elements Oxygen and Hydrogen. The properties of a drop of water will depend on the simplest unit of water, which is the water molecule . Therefore, the smallest unit of the water drop that retains all the physical and chemical properties exhibited by a sample of water is the molecule.
According to this formula : ㏑[A] /[Ao] = - Kt when we have Ao = 0.3 m and K =0.46 s^-1 t = 20min = 0.2 x 60 =12 s So by substitution : ㏑[A] / 0.3 = - 0.46 * 12 ㏑[A] / 0.3 = - 5.52 by taking e^x for both side of the equation we can get [A] ∴[A] = 0.0012 mol dm^-3
