Let's address each part of the question step by step.
### Part A: Unit of Reaction Rates in Solution
The unit commonly used to express the rates of reactions occurring in solution is Moles per second (M/s). This is because reaction rates are typically measured based on changes in concentration of reactants or products over time, and concentration is usually expressed in moles per liter (M). Combining this with time measured in seconds gives us the unit M/s.
Thus, the correct choice is:
- M/s
### Part B: Effect of Temperature on Reaction Rate
Generally, as the temperature increases, the reaction rate also increases. This is because higher temperatures provide more kinetic energy to the reactants, which increases the frequency and energy of collisions between reactant molecules, often leading to a higher probability of successful collisions that result in a reaction.
Thus, the correct choice is:
- As temperature increases, reaction rate increases.
### Part C: Instantaneous Reaction Rate as a Reaction Proceeds
As a reaction proceeds, the concentration of reactants typically decreases, which in many cases leads to a decrease in the reaction rate. This is because fewer reactant molecules are available to collide and react with each other.
Thus, the correct choice is:
- As a reaction proceeds, the instantaneous reaction rate decreases.
### Conclusion:
- Part A: The unit usually used to express the rates of reactions occurring in solution is M/s.
- Part B: As the temperature increases, reaction rate increases.
- Part C: As a reaction proceeds, the instantaneous reaction rate decreases.
These insights help to understand the general behavior of chemical reactions and the conditions that affect their rates.
