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Worksheet: The Contact Process

Q1:

When sulfur dioxide reacts with oxygen gas to form sulfur trioxide, energy is absorbed when bonds are broken and released when bonds are formed. The S O bonds in sulfur dioxide have an energy of 522 kJ/mol, while those in sulfur trioxide have an energy of 495 kJ/mol. The O O double bond in oxygen has an energy of 494 kJ/mol. Determine whether the reaction is endothermic or exothermic and calculate the total energy change per mole of sulfur dioxide.

  • AEndothermic, 301 kJ/mol
  • BEndothermic, 53 kJ/mol
  • CExothermic, 329 kJ/mol
  • DExothermic, 1 9 4 kJ/mol
  • EExothermic, 8 2 kJ/mol

Q2:

One step of the contact process involves a transition metal catalyst. In what range of pressures is this reaction typically performed?

  • A 4–10 atm
  • B 2–4 atm
  • C 10–20 atm
  • D 1–2 atm
  • E 20–50 atm

Q3:

A catalyst is used in one step of the contact process. What feature of the reaction is affected by the catalyst?

  • AMaximum reaction yield
  • BPosition of equilibrium
  • CProduct purity
  • DReaction rate
  • EEnergy released by the reaction

Q4:

A sample of pure material produced by the contact process contains 15.0 kg of sulfur atoms.

How many moles of the product does the sample contain?

What is the total mass of the product sample?

Q5:

Give a balanced chemical equation for the final step of the contact process.

  • A S O + H S O H S O 3 2 4 2 2 7
  • B H S O + H O 2 H S O 2 2 5 2 2 3
  • C S O + H S O 2 H S O 2 2 3 2 2 5
  • D H S O + H O 2 H S O 2 2 7 2 2 4
  • E H S O + 2 H O 2 H S O 2 4 2 2 3

Q6:

In one step of the contact process, a gaseous compound containing sulfur and oxygen is reacted with a large excess of oxygen gas.

Why is it beneficial to use a large excess of oxygen gas?

  • AAll of the sulfur-containing reactant is converted to product.
  • BThe product is already mixed with oxygen for the next reaction step.
  • CThe yield of unwanted side reactions is reduced.
  • DThe maximum percentage yield of product is increased.
  • EThe reaction rate is increased.

Why would it be disadvantageous to increase the amount of oxygen further, while keeping the total reactant gas pressure fixed?

  • AThe final quantity of product is reduced.
  • BA larger amount of oxygen gas is wasted.
  • CMore highly oxidized products are formed.
  • DThe maximum percentage yield of product is reduced.
  • EThe risk of an explosive reaction is increased.

Q7:

During one step of the contact process, a transition metal compound, A , reacts with a compound containing sulfur and oxygen, B . What happens during this reaction?

  • A B binds to A and reacts with a molecule of oxygen.
  • BAn oxygen atom is transferred from B to A .
  • C B binds to A and reacts with a molecule of water.
  • DAn oxygen atom is transferred from A to B .
  • EA water molecule is transferred from A to B .

Q8:

One step of the contact process involves a transition metal catalyst. At what temperature is this reaction typically performed?

Q9:

In one of the steps of the contact process, a compound containing sulfur and oxygen is reacted with excess oxygen in the presence of a catalyst. Which material is typically used as the catalyst in this reaction?

  • A V O 3
  • B V O 5
  • C V O
  • D V O 2 5
  • E V O 2 3

Q10:

One step of the contact process involves a transition metal catalyst. Why would it be disadvantageous to conduct this reaction at a higher gas pressure?

  • AIncreasing the gas pressure increases the equilibrium yield but lowers the reaction rate.
  • BIncreasing the gas pressure increases the reaction rate but lowers the equilibrium yield.
  • CIncreasing the gas pressure lowers both the equilibrium yield and the reaction rate.
  • DIncreasing the gas pressure requires more expensive equipment.
  • EIncreasing the gas pressure increases the yield of unwanted by-products.

Q11:

Give a balanced chemical equation for the reaction used to convert elemental sulfur ( S ) 8 to a sulfur-containing gas for use as a reactant in the contact process.

  • A S + 8 H O + 1 2 O 8 H S O 8 2 2 2 4
  • B S + 1 2 O 8 S O 8 2 3
  • C S + 8 H O + 8 O 8 H S O 8 2 2 2 3
  • D S + 8 O 8 S O 8 2 2
  • E S + 4 H O + 1 2 O 4 H S O 8 2 2 2 2 7

Q12:

Give a balanced chemical equation for the second oxidation step of the contact process.

  • A S + O S O 2 2
  • B 2 S + 3 O 2 S O 2 3
  • C S O + H S O H S O 3 2 4 2 2 7
  • D 2 S O + O 2 S O 2 2 3
  • E S O + H O H S O 2 2 2 3

Q13:

In a key step of the contact process, two molecules of compound A react reversibly with one molecule of compound B to form two molecules of compound C : Compounds A , B , and C are all gaseous at the reaction temperature.

Identify compound B .

  • A S O 2
  • B H O 2
  • C S O 3
  • D O 2
  • E H S O 2 4

Identify compound C .

  • A S O 3
  • B H O 2
  • C O 2
  • D S O 2
  • E H S O 2 4

What happens to the reaction rate and the percentage yield of C if the total gas pressure increases?

  • AThe reaction rate increases and the percentage yield of C does not change.
  • BThe reaction rate and percentage yield of C both decrease.
  • CThe reaction rate and percentage yield of C both increase.
  • DThe reaction rate increases and the percentage yield of C decreases.
  • EThe reaction rate decreases and the percentage yield of C increases.

What happens to the reaction rate and the percentage yield of C if the reaction temperature increases?

  • AThe reaction rate increases and the percentage yield of C decreases.
  • BThe reaction rate decreases and the percentage yield of C increases.
  • CThe reaction rate increases and the percentage yield of C does not change.
  • DThe reaction rate and percentage yield of C both increase.
  • EThe reaction rate and percentage yield of C both decrease.

Q14:

Give a balanced chemical equation for the reaction used to convert pyrite ( F e S ) 2 to sulfur dioxide for use as a reactant in the contact process.

  • A 2 F e S + 5 O F e O + 4 S O 2 2 2 3 2
  • B 2 F e S + 5 O 2 F e O + 4 S O 2 2 2
  • C 4 F e S + 7 O 2 F e O + 4 S O 2 2 2 3 2
  • D 4 F e S + 1 1 O 2 F e O + 8 S O 2 2 2 3 2
  • E 4 F e S + 9 O 4 F e O + 8 S O 2 2 2

Q15:

Which of the following compounds is not formed as a major product during one of the steps of the contact process?

  • A S O 3
  • B S O 2
  • C H S O 2 4
  • D H S O 2 2 5
  • E H S O 2 2 7

Q16:

One step of the contact process involves a reversible reaction.

Which of the following is the best definition of a reversible reaction?

  • AA reversible reaction is one in which the products are less thermodynamically stable than the reactants.
  • BIn a reversible reaction, the products convert slowly back to reactants after the reaction is complete.
  • CA reversible reaction is one in which the final reaction mixture contains both reactants and products.
  • DA reversible reaction is one in which some product molecules are converted back to the reactants.
  • EIn a reversible reaction, the energy released during the conversion of reactants to products is close to zero.

What name is given to the theory used to predict changes in the percentage yield of a reversible reaction?

  • ALe Chatelier’s principle
  • BGibbs’s phase rule
  • CBoyle’s law
  • DDalton’s law
  • EClausius–Clapeyron relation

Which of the following has no effect on the percentage yield of a reversible reaction?

  • AReaction solvent
  • BTemperature
  • CCatalyst
  • DPressure
  • EReactant concentration

Q17:

Why is it impractical to produce sulfuric acid from sulfur trioxide directly?

  • ASulfur trioxide forms a solution in water but does not react.
  • BThe reaction of sulfur trioxide with oxygen is highly exothermic.
  • CSulfur trioxide is too unreactive to be oxidized by air.
  • DThe reaction of sulfur trioxide with water is highly exothermic.
  • EThe reaction of sulfur trioxide with oxygen is highly endothermic.

Q18:

One step of the contact process involves a transition metal catalyst. Why would it be disadvantageous to conduct this reaction at a lower gas pressure?

  • ADecreasing the gas pressure increases the equilibrium yield but lowers the reaction rate.
  • BDecreasing the gas pressure increases the reaction rate but lowers the equilibrium yield.
  • CDecreasing the gas pressure increases the yield of unwanted by-products.
  • DDecreasing the gas pressure lowers both the equilibrium yield and the reaction rate.
  • EDecreasing the gas pressure requires more expensive equipment.

Q19:

Oxygen gas is used as a reactant in a number of steps of the contact process.

How many molecules of oxygen gas react per atom of sulfur in the final product?

What mass of oxygen gas is needed to produce 23.0 metric tons of the pure product?