Rate of Reaction Quiz
Questions: 16 · 10 minutes
1. A reaction is repeated using a more concentrated solution while all other conditions remain unchanged. Why does its rate usually increase?
Each reacting particle gains more mass in the concentrated solution
There are more reactant particles in a given volume, so collisions occur more frequently
The products require less energy to form because less solvent is present
The concentrated solution always has a higher final temperature
2. In a clock reaction, a student measures the time taken for a fixed visible change to occur. If every trial uses the same endpoint, which quantity can be used as a simple measure of relative rate?
One divided by the endpoint time, with larger values representing faster rates
The final temperature divided by the endpoint time
The endpoint time itself, with larger values representing faster rates
The endpoint time multiplied by the total solution volume
3. What does the rate of a chemical reaction describe?
The total amount of product present when the reaction ends
The amount of reactant used up or product formed per unit time
The energy stored in the reactants before they collide
The time required for every reversible reaction to reach equilibrium
4. A reaction produces 60 cm³ of gas during its first 30 seconds. What is its average rate of gas production over that period?
2 cm³/s
0.5 cm³/s
30 cm³/s
1,800 cm³/s
5. According to collision theory, when can a collision between reacting particles lead to a reaction?
Whenever the particles touch, regardless of their energy or orientation
When the particles collide at a temperature above the boiling point
Only when the particles have identical masses and speeds
When the particles collide with sufficient energy and a suitable orientation
6. A student investigates how hydrochloric acid concentration affects its reaction with calcium carbonate chips. Which pair of conditions should be kept the same for a fair comparison?
The volume of gas collected and the reaction rate
The acid concentration and the time taken for the reaction
The mass and particle size of the calcium carbonate
The calcium carbonate surface area and the acid concentration
7. A student reacts magnesium ribbon with dilute hydrochloric acid. Which method most directly measures the rate at which hydrogen is produced?
Collect the gas in a gas syringe and record its volume at regular times
Measure the original length of magnesium ribbon with a ruler
Record the solution's pH only after the reaction has finished
Evaporate the final mixture and weigh the remaining salt
8. Two identical reactions are run at 20°C and 40°C. Why is the reaction usually faster at 40°C?
The particles become larger, so each collision produces more product
The activation energy becomes zero at the higher temperature
Heating increases the amount of reactant without changing its concentration
Particles move faster, causing more frequent collisions and a greater proportion of successful collisions
9. In two trials, the same reaction produces the same final volume of gas. Trial B reaches that volume sooner than Trial A. Which observation best supports the idea that Trial B used a catalyst?
Trial B produces gas more quickly but reaches the same final volume
Trial B begins at a higher temperature and stays hotter throughout
Trial B starts with a larger mass of reactant and finishes with more gas
Trial B produces no gas until the catalyst has been completely used up
10. How does a catalyst increase the rate of a reaction?
It raises the energy of every reactant particle by the same amount
It provides an alternative reaction pathway with a lower activation energy
It increases the final amount of product by becoming part of that product
It shifts every reversible reaction completely toward the products
11. Four trials produce the same fixed amount of product in 25 s, 40 s, 55 s, and 70 s. Which trial has the greatest average rate?
The 70-second trial, because the reaction lasts longest
The 55-second trial, because its time is closest to the average
The 25-second trial, because the same amount forms in the shortest time
All four trials, because they produce the same final amount
12. What is activation energy?
The total energy released after all reactants have become products
The energy needed to maintain a reaction at equilibrium
The average kinetic energy of all particles in a reaction mixture
The minimum energy that colliding particles need for a reaction to occur
13. Why can increasing the pressure speed up a reaction between gases at constant temperature?
It lowers the mass of each gas particle, allowing easier movement
It guarantees that every collision has energy above the activation energy
It forces gas particles closer together, increasing collision frequency
It converts some of the gas into a catalyst for the reaction
14. Why does a reaction commonly slow down as it proceeds in a closed mixture?
The activation energy steadily increases as products form
The catalyst, if present, must always be consumed before the reactants
Particles gradually stop moving once the first product appears
Reactants are used up, so their particles collide successfully less often
15. Equal masses of calcium carbonate react separately with identical hydrochloric acid solutions. Why does powdered calcium carbonate usually react faster than large chips?
The powder contains more calcium carbonate despite having the same mass
The powder has a larger surface area exposed to the acid
The chips increase the activation energy of the reaction
The powder raises the acid concentration when it is added
16. The volume of gas produced is 0 cm³ at 0 seconds, 24 cm³ at 10 seconds, 40 cm³ at 20 seconds, 48 cm³ at 30 seconds, and 50 cm³ at 40 seconds. During which interval is the average reaction rate greatest?
From 30 to 40 seconds
From 20 to 30 seconds
From 0 to 10 seconds
From 10 to 20 seconds