Catalysts assignment and quiz

Consider the energy diagram below. mc022-1.jpg Which statement best describes the diagram? The catalyzed reaction passes through C. The energy of the catalyst is shown by A. The reaction pathway through B is faster. The energy of the reactants with catalyst is at D.

The catalyzed reaction passes through C.

Which of the following statements describes how enzymes differ from ordinary chemical catalysts? Enzymes are inorganic in nature. Enzymes catalyze select chemical reactions. Enzymes bind their substrates for a brief time. Enzymes increase the rate of a chemical reaction.

Enzymes catalyze select chemical reactions.

Which catalyzed reaction breaks up ozone? 2H2O2(l) → 2H2O(l) + O2 O3 + O → 2O2 2H2O2 (aq) → 2H2O(l) + O2 O2 + 2SO2 → 2SO3

O3 + O → 2O2

Hydrogen gas reacts rapidly with oxygen gas in the presence of a platinum catalyst. Which equation correctly represents this reaction? H2(g) + O2(g) + Pt → H2(g) + O2(g) H2(g) + O2(g) → H2(g) + O2(g) + Pt 2H2(g) + O2(g) →/Pt 2H2O(g) + Pt 2H2(g) + O2(g) →/Pt 2H2O(g)

2H2(g) + O2(g) →/Pt 2H2O(g)

A reaction is shown below. Reaction : 2H2O2(l) →/ MnO2(s) 2H2O(l) + O2(g) What can be concluded about this reaction? A homogeneous catalyst is being used in the reaction. A heterogeneous catalyst is being used in the reaction. A catalyst is not being used in this reaction. An enzyme is being used in this reaction.

A heterogeneous catalyst is being used in the reaction.

Although expensive, platinum is used as a catalyst to break down harmful gases in car exhaust into less harmful gases. Which statement best describes platinum in this use? It is a homogeneous catalyst, so only a small amount is needed even though it exits with the products. It is a heterogeneous catalyst, so only a small amount is needed and it is easily separated from the products. It is a homogeneous catalyst, so although a large amount is needed, it is easily separated from the products. It is a heterogeneous catalyst, so a large amount is needed and it exits with the products.

It is a heterogeneous catalyst, so only a small amount is needed and it is easily separated from the products.

Which statement defines activation energy? It is the sum of the maximum energy and reactant energy. It is the sum of the product energy and reactant energy. It is the difference between reactant energy and maximum energy. It is the difference between product energy and reactant energy.

It is the difference between reactant energy and maximum energy.

What overall effect does adding a catalyst have on a chemical reaction? It increases pressure on the system. It increases reactant surface area. It lowers the activation energy that is needed. It lowers the concentration of reactants.

It lowers the activation energy that is needed.

The second reaction in the formation of sulfuric acid occurs slowly. mc011-1.jpg NO2 is added to the reaction to speed it up. In which form would this substance be a homogeneous catalyst for this reaction? NO2(g) NO2(l) NO2(s) NO2(aq)

NO2(g)

Why are enzymes required for living things to function? Reactions take place too slowly at body temperature and must be speeded up. Reactions take place too quickly at body temperature and must be slowed down. Reactions in the body require enzymes to act as reactants. Reactions in the body produce enzymes as byproducts.

Reactions take place too slowly at body temperature and must be speeded up.

Sulfuric acid was once produced through the reaction of sulfur trioxide with water. Sulfur trioxide can form through the reaction of sulfur dioxide and oxygen gas. When nitrogen monoxide gas is added to the system, the reaction speeds up significantly because it proceeds through the following steps: 2NO(g) + O2(g)→2NO2(g) 2NO2(g) + 2SO2(g) → 2NO(g) + 2SO3(g) Identify the catalyst in this reaction, explain how you know it is the catalyst, and describe how it increases the rate of the reaction.

Which of the following did your answer include? NO is the catalyst. NO is the catalyst because it increases the rate of the reaction but is not consumed during the reaction. NO increases the rate of the reaction by lowering the activation energy. The reaction of NO with O2 provides an alternative reaction pathway with a lower activation energy.

The hydrogenation of unsaturated hydrocarbons is an important industrial process. Precious metals, such as platinum and palladium, can greatly increase the rate of this reaction. During this process, the gaseous reactants are pumped across a layer of metal powder. An example of this process is shown below. Hydrogenation on catalyst Describe how the metal probably increases the reaction rate, identify whether this is an example of homogeneous or heterogeneous catalysis, and explain how you know.

Which of the following did your answer include? The metal probably increases reaction rate by either holding reactant molecules in the correct orientation to react or by weakening or breaking bonds in reactant molecules to make them more reactive. This is an example of heterogeneous catalysis. It is heterogeneous catalysis because the catalyst is a solid and the reactants are gases. In heterogeneous catalysis, the catalyst is in a different phase than the reactants.

Urea is a product of digestion of proteins and other foods that contain nitrogen. It can react with water and acid to form ammonium ions and bicarbonate ions according to the equation below: reaction energy diagram The enzyme urease catalyzes this reaction. If urease is added to a solution that contains ammonia and other nitrogen-containing compounds (but no urea), will the urease catalyze any reactions? Explain your answer.

Which of the following did your answer include? Urease is an enzyme. Enzymes are highly specific in the reactions they catalyze. Enzymes can typically bind only to the substrate(s) for the reaction they catalyze. If the solution contains no urea, urease will not bind to any of the substances in the solution, so it will not catalyze any reactions in the solution.