Which substance is a raw material used to manufacture sulfuric acid?
A) vanadium(V) oxide
B) sulfur
C) sulfur dioxide
D) sulfur trioxide
▶️ Answer/Explanation
Ans: B
Sulfur is the primary raw material used in the Contact Process for manufacturing sulfuric acid. The process begins by burning sulfur in air to produce sulfur dioxide (SO₂). While vanadium(V) oxide is used as a catalyst in the process, it’s not a raw material. Sulfur dioxide and sulfur trioxide are intermediate products in the process, not the starting materials.
Sulfur dioxide is converted to sulfur trioxide in the Contact process.
The conditions used are 450 °C and 200 kPa with a vanadium(V) oxide catalyst.
Which row describes and explains the effect of changing conditions on the rate of reaction?
| change in conditions | effect on rate | explanation | |
|---|---|---|---|
| A | no catalyst | lower | the activation energy is higher |
| B | higher pressure | higher | the particles have more kinetic energy |
| C | lower temperature | lower | the particles collide more frequently |
| D | lower pressure | higher | there are more particles per unit volume |
▶️ Answer/Explanation
Ans: A
Analyzing each option:
A) Correct – Without a catalyst, the activation energy would be higher, resulting in a lower rate of reaction.
B) Incorrect – While higher pressure does increase the rate, the explanation is wrong (it’s because there are more frequent collisions, not because particles have more kinetic energy).
C) Incorrect – Lower temperature does decrease the rate, but the explanation is wrong (particles collide less frequently at lower temperatures).
D) Incorrect – Lower pressure decreases the rate (fewer particles per unit volume).
The catalyst provides an alternative reaction pathway with lower activation energy, so removing it would increase the activation energy and decrease the rate.
Which reaction pathway diagram is correctly labelled?
A) 
B) 
C) 
D) 
▶️ Answer/Explanation
Ans: A
A correctly labeled reaction pathway diagram should show:
- Reactants at a certain energy level
- Products at a different energy level (lower for exothermic, higher for endothermic)
- Activation energy (Eₐ) as the energy difference between reactants and the transition state
Option A is correct because:
- It clearly shows the reactants at a higher energy level than products (indicating an exothermic reaction)
- The activation energy (Eₐ) is correctly marked as the energy barrier between reactants and the transition state
- The progress of reaction is properly indicated on the x-axis
The other options likely have incorrect labeling of Eₐ or the relative positions of reactants and products.
Question
The equation for the manufacture of ammonia in the Haber process is shown.
\(3H_{2}(g) + N_{2}(g)\rightleftharpoons 2NH_{3}(g)\)
The forward reaction is exothermic.
Which row describes the effect of the stated change on the reaction rate and the yield of ammonia?
Answer/Explanation
Ans:
B