Answer:
The correct option is a
Step-by-step explanation:
Factors that affect the rate of chemical reactions are
- surface area of reactants (solid)
- temperature
- pressure
- presence of catalyst
- concentration
The focus here will be on the options provided in the question (starting from option d)
Adding more of a substance to a mixture has nothing to do with a chemical reaction because a mixture is a combination of two or more substances that are physically combined (NOT chemically combined) and as such, the reaction rate cannot be determined/altered.
Increasing the concentration of the reactants leads to an increase in the rate of reaction as more product will be formed as a result of this. This is so because the molecules will be able to interact better because of the increase in the number of molecules present in the reaction.
Raising the temperature of a reaction causes for effective collision which causes an increase in the rate of reaction. In chemical reactions, not all collisions leads to a reaction, the collision that causes molecules to react is what is referred to as effective collision.
Lowering the pressure of a gaseous reaction reduces the number of effective collisions and hence slows down the rate of chemical reaction. This makes option a the correct option