Worksheet: The Contact Process

In this worksheet, we will practice describing the production of sulfuric acid in the contact process and explaining the choices of reaction conditions.

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 SO bonds in sulfur dioxide have an energy of 522 kJ/mol, while those in sulfur trioxide have an energy of 495 kJ/mol. The OO 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.

  • AExothermic, 82 kJ/mol
  • BEndothermic, 53 kJ/mol
  • CExothermic, 329 kJ/mol
  • DExothermic, 194 kJ/mol
  • EEndothermic, 301 kJ/mol

Q2:

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?

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

Q3:

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

Q4:

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

  • A4–10 atm
  • B2–4 atm
  • C20–50 atm
  • D1–2 atm
  • E10–20 atm

Q5:

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

Q6:

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

Q7:

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

Q8:

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

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

Q9:

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

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

Q10:

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

  • APosition of equilibrium
  • BReaction rate
  • CEnergy released by the reaction
  • DProduct purity
  • EMaximum reaction yield

Q11:

One step of the contact process involves a reversible reaction.

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

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

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

  • AGibbs’s phase rule
  • BBoyle’s law
  • CLe Chatelier’s principle
  • DClausius–Clapeyron relation
  • EDalton’s law

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

  • ATemperature
  • BCatalyst
  • CPressure
  • DReactant concentration
  • EReaction solvent

Q12:

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: 2A+B2C. Compounds A, B, and C are all gaseous at the reaction temperature.

Identify compound B.

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

Identify compound C.

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

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 increase.
  • CThe reaction rate decreases and the percentage yield of C increases.
  • DThe reaction rate increases and the percentage yield of C decreases.
  • EThe reaction rate and percentage yield of C both decrease.

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

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

Q13:

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

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

Q14:

Oxygen gas is used as a reactant in a number of steps of the contact process. Assume sulfur is the starting material.

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?

Q15:

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?

Q16:

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

Q17:

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?

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

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

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

Q18:

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

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

Q19:

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

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

Q20:

A catalyst, C, increases the rate of a reaction by providing a lower-energy pathway between the reactants, R1 and R2, and the product, P. The reaction may involve an intermediate, I. Which of the shown graphs best illustrates the behavior of the transition metal catalyst in the contact process?

  • A
  • B
  • C
  • D
  • E

Q21:

What is the end product of the contact process?

  • ASulfur trioxide
  • BNitric acid
  • CMargarine
  • DSulfuric acid
  • EAmmonia

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