Reaction rates depend on collisions between particles. If a particular reactant is involved in the rate determining step for a reaction, an increase in the number of its particles in solution will also result in an increase in the rate. The number of particles of a reactant in solution can be measured by the concentration of that reactant in mol L
-1.
The concentrations of the reactants in the reaction mixture are used to calculate reaction rate and to deduce the rate law. These concentrations are calculated as homework.
Concentration measures the
amount of solute (substance dissolved) in a
volume of solution.
The chemists' unit of amount is mole (n). 1 mol of a substance is 6.02 x 1023 formula units. The concentration of a solute in mol L-1 is calculated by dividing the amount in moles of solute dissolved by the TOTAL volume of the solution in litres.
How do I calculate the amount in moles of a particular solute?
The reaction mixture is prepared by mixing several solutions of different solutes. Before reaction occurs, the amount in moles of each solute in the mixed solution is the same as in its solution before mixing. This is calculated by multiplying the concentration of the solution mixed (in mol L-1) by its volume (in L).
What is the total volume?
The total volume of the reaction mixture is the sum of the volumes of the solutions mixed.