Look at the graph. At what time does the reaction finish?

• 4 minutes

• 5 minutes

• 6 minutes

• 7 minutes

Answer explanation

The graph indicates that the reaction reaches completion at 5 minutes, as this is the point where the curve levels off, indicating no further change in the reaction progress.

The decomposition of hydrogen peroxide is catalysed by adding a small amount of manganese (IV) oxide. Which of the graphs below shows the mass of the catalyst as the reaction takes place?

• A

• B

• C

• D

Answer explanation

The mass of the catalyst, manganese (IV) oxide, remains constant throughout the reaction as it is not consumed. Graph C correctly shows a horizontal line, indicating no change in mass over time.

Which two of these lines on the graph has the highest rate of reaction?

• A

• B

• C

• D

Answer explanation

Lines A and B show the steepest slopes on the graph, indicating they have the highest rate of reaction. A steeper slope corresponds to a faster change in concentration over time, reflecting a quicker reaction rate.

Which of these reaction lines on the graph produces the most product by the end of the reaction?

• A

• B

• C

• D

Answer explanation

Reaction line A produces the most product by the end of the reaction, as it reaches the highest point on the graph compared to lines B, C, and D, indicating a greater amount of product formed.

Which of these reaction lines on the graph has the slowest reaction rate?

• A

• B

• C

• D

Answer explanation

Reaction line D has the slowest reaction rate as it shows the least steep slope on the graph, indicating a slower change in concentration over time compared to lines A, B, and C.

A student measures the rate of a chemical reaction and produces line A on the graph. In the second reaction,B, what are they likely to have changed about the reaction?

• Decreased the concentration of one of the reactants by half

• Doubled the concentration of one of the reactants

• Increased the temperature of the reaction

• Decreased the temperature of the reaction

Answer explanation

Decreasing the concentration of a reactant typically slows down the reaction rate, which aligns with the change observed in line A compared to line B. This is why the correct choice is to decrease the concentration by half.

This is the graph of 3 reactions. Which reaction has the fastest rate?

This is the graph of 3 reactions. Which reaction has the slowest rate?

Answer explanation

The graph indicates that Reaction 3 has the lowest rate, as it shows the least steep slope compared to the other reactions. Therefore, Reaction 3 is the correct choice for the slowest rate.

In which reaction (2 or 3) what the concentration of the limiting reactant HALF that of reaction 1?

Answer explanation

In reaction 1, the limiting reactant concentration is at a certain level. For reaction 2, it remains the same, while in reaction 3, it is half that of reaction 1, making the correct answer 3.

Which two reactions produce the same volume of carbon dioxide by the end of the reaction?

• 1

• 2

• 3

• you cannot tell