When the concentration of hydrogen chloride (HCl) molecules is doubled in the reaction between calcium carbonate (CaCO₃) and HCl, several important changes occur at a molecular level:
1. Number of Collisions Between Reactants:
- According to collision theory, the rate of a chemical reaction depends on the number of effective collisions between reactant molecules.
- When the concentration of HCl is doubled, there are more HCl molecules present in a given volume.
- This leads to an increased frequency of collisions between HCl molecules and CaCO₃ molecules.
2. Rate of the Forward Reaction:
- An increase in the concentration of reactants generally leads to an increased rate of the forward reaction.
- With more frequent effective collisions (collisions that have the proper energy and orientation to lead to a reaction), the rate at which products are formed (CaCl₂, CO₂, and H₂O) will increase.
Thus, when the hydrogen chloride concentration is doubled:
When the hydrogen chloride concentration doubles, the number of collisions between the reactants increases and the rate of the forward reaction increases.
So, the correct and complete statement is:
When the hydrogen chloride concentration doubles, the number of collisions between the reactants increases and the rate of the forward reaction increases.
