Catalysts

Another type of graph can be used when assessing rate of reaction. This graph shows the energy available in the reactant particles and indicates the proportion of them that have the required energy for a reaction.

To compare rate of reaction at different temperatures accurately the Arrhenius equation is used. A is the exponential factor, which relates to the frequency of particle collisions. K is the rate constant and is proportional to rate of reaction. ln is used to solve the Arrhenius equation to remove the 'e' from the equation, ln is a function on your calculator and you don't need to understand it further for chemistry.

A catalyst is a substance that lowers the activation energy of a reaction by providing an alternative pathway for reaction. The catalyst doesn't take part in the reaction so will not be altered or used up.

Catalysts are important to many industrial and biological reactions (inside plants or animals). Biological catalysts are given the name 'enzyme' and different enzymes are present in every cell of the human body to perform a number of vital reactions.

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What is the term given to the required energy for a reaction?

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This graph shows the energy of the reactant particles in the reaction between zinc and hydrochloric acid. What factor could be responsible for the difference between the two lines?

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This graph shows the energy of the reactant particles in the reaction between zinc and hydrochloric acid. What factor could be responsible for the difference between the two lines?

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Which letter on this graph indicates the activation energy of this reaction?

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Which number on this graph indicates the activation energy of this reaction?

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What is shown by each of the labels on this reaction profile diagram for an exothermic reaction?

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What factor would result in a higher proportion of particles having the activation energy?

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What factor would result in more reactant particles being present in the reaction space?

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Which number from the Arrhenius equation is used when comparing rate of reaction of two experiments, k, A, Ea, R or T?

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What is temperature usually measured in for the Arrhenius equation?

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Which of the variables in the Arrhenius equation will remain the same when the same reaction is repeated at a different temperature?

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Which of the variables in the Arrhenius equation will change when the same reaction is repeated at a different temperature?

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In the reaction between oxygen and nitrous oxide at 200K the activation energy is 124000 J/mol and the rate constant is 1.3 x 10-10 s-1. Calculate the exponential factor (A) for this experiment at 200K.

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In the reaction between hydrogen and nitrogen at 50C the activation energy is 162 kJ/mol and the rate constant is 2.0 x 10-9 s-1. Calculate the exponential factor (A) for this experiment at 200K.

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In the reaction between oxygen and nitrous oxide at 250K the activation energy is 124 kJ/mol and the exponential factor (A) is 3.28 x 1022 s-1. Calculate the rate constant for this experiment at 250K.

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In the reaction between hydrogen and nitrogen at 40C the activation energy is 162 kJ/mol and the rate constant is 2.0 x 10-9 s-1. Calculate the exponential factor (A) for this experiment at 250K.

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How do catalysts affect rate of reaction using collision theory?

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Manganese oxide acts as a catalyst for the decomposition of hydrogen peroxide, what would be the effect of adding manganese oxide on the volume of oxygen produced in the first 10 seconds of this reaction?

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Which of the lines in this reaction profile diagram show the reaction when a catalyst is used?

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Manganese oxide acts as a catalyst for the decomposition of hydrogen peroxide, what would be the effect of adding manganese oxide on the volume of oxygen produced by the end of this reaction (using the same amount of hydrogen peroxide)?

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What section of the periodic table contains the elements that usually act as catalysts?

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Why do transition metals make good catalysts?

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Why do group 1 metals make poor catalysts?

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What is the general mechanism of catalysis?

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Give an example of what enzymes may be useful for in human cells

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Why are enzymes present in the human gut?

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Look at this graph showing enzyme activity at different temperatures. Why does the rate of reaction fall at higher temperatures and not continue to increase?

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Where else might enzymes be used other than in plants or animals?

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Yeast contains enzymes that cause fermentation of sugars, how is this used in industry?

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What is the catalyst used in the Haber process? (the reaction between nitrogen and hydrogen to form ammonia)

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What is the catalyst used in the contact process? (a step in the synthesis of sulphuric acid)

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What is the catalyst used in the decomposition of hydrogen peroxide?

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