Observe: Change the Surface area from Minimum to Maximum. You can imagine that a

solid reactant has been dissolved in a liquid.

How does this change how many Reactant B molecules are exposed to Reactant A?

Changing the surface area from minimum to maximum increases the number of reactants in a chemical reaction.

An increase in surface area of a solid reactant means more of its particles are exposed to attack by the other Particle. This results in an increased chance of collisions between reactant particles, so there are more collisions in any given time and the rate of reaction increases.

i do not get it   at all

a saline water is fed to a reverse osmosis unit at flow rate o rotameter connected to reject (retentate) line reads 8 installed in reject and permeate line reads 15.2 milli siemens/cm and 300 micro siemens/com respectively.