1. Adding a catalyst increases the rate of a reaction. If the rate increases, th
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Question
1. Adding a catalyst increases the rate of a reaction. If the rate increases, then either k increases or the order of the reaction changes. what experiments might you perform to discover which is occurring?
2. In the method of initial rates, only a small amount of reagent is used up (the change in concentration is small compared to the total concentration). The elapsed time is used to calculate the rate. Why is this more accurate than calculating the rate from the amount of time required to use up all of the reagent? (HintL What happens as the concentration decreases?)
3. If k changes due to the presence of a catalyst (at a constant temperature), what factors in the Arrhenius equation may have changed? What experiments might you perform to discover what has changed?
Explanation / Answer
1. A catalyst is a substance which speeds up a reaction, but is chemically unchanged at the end of the reaction. When the reaction has finished, you would have exactly the same mass of catalyst as you had at the beginning.
k increases while the order of the reaction remain unchange.
Some examples
Reaction Catalyst
Decomposition of hydrogen peroxide manganese(IV) oxide, MnO2
Nitration of benzene concentrated sulphuric acid
Manufacture of ammonia by the Haber Process iron
Hydrogenation of a C=C double bond nickel
3. A catalyst is usually defined as a substance that speeds up a reaction without being consumed by it. More specifically, a catalyst provides an alternative, lower activation energy pathway between reactants and products. As such, they are vitally important to chemical technology; approximately 95% of industrial chemical processes involve catalysts of various kind. In addition, most biochemical processes that occur in living organisms are mediated by enzymes, which are catalysts made of proteins.
It is important to understand that a catalyst affects only the kinetics of a reaction; it does not alter the thermodynamic tendency for the reaction to occur.
The molecular entity that emerges from each step may be a final product of the reaction, or it might be an intermediate
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