Chapter 9 Review Gr 10 SABIS K-chemistry.com Mr. Hisham Mahmoud

List four factors that affects the rate of a reaction

• Temperature

• Concentration of reactants

• Surface area of contact

• Pressure of gaseous reactants

• catalysts

Answer explanation

Factors affecting the rate of a chemical reaction?

a) Concentration of reactants

b) Pressure of gaseous reactants

c) Surface area of contact in case of heterogeneous systems

d) Temperature

e) Nature of substances reacting

f) Catalysts

When magnesium ribbon reacted with excess dilute hydrochloric acid at room temperature, the total volume of hydrogen produced was noted every 20 seconds.

The results obtained are given in the graph labeled C

drawn below

Which of the graphs A, B, D or E would have been obtained if:

Leakage of gas during the experiment

• A

• B

• D

• E

Answer explanation

If there is a leakage then H2 gas would escape. As a result the collected volume will be much less.

When magnesium ribbon reacted with excess dilute hydrochloric acid at room temperature, the total volume of hydrogen produced was noted every 20 seconds.

The results obtained are given in the graph labeled C

drawn below

Which of the graphs A, B, D or E would have been obtained if:

Only half the magnesium ribbon had been used as compared with the original amount used in C?

• A

• B

• D

• E

Answer explanation

D

Starting with half the mass of Mg results in the formation of half the volume of H₂. As production of hydrogen gas occurs in a 1:1 ratio with consumption of Mg.

When magnesium ribbon reacted with excess dilute hydrochloric acid at room temperature, the total volume of hydrogen produced was noted every 20 seconds.

The results obtained are given in the graph labeled C

drawn below

Which of the graphs A, B, D or E would have been obtained if:

Slightly warmer excess acid had been used?

• A

• B

• D

• E

Answer explanation

Slightly warming the mixture will increase the energy of the particles and their speeds. As a result the frequency of effective collisions will increase. This will increase the rate which is shown by a steeper rise. However, the starting amount of Mg is the same so the final volume of

H₂ remains the same.

When magnesium ribbon reacted with excess dilute hydrochloric acid at room temperature, the total volume of hydrogen produced was noted every 20 seconds.

The results obtained are given in the graph labeled C

drawn below

Which of the graphs A, B, D or E would have been obtained if:

A greater mass of powdered magnesium had been used?

• A

• B

• D

• E

Answer explanation

A greater mass of Mg results in the formation of a greater volume of H₂.Powdering the Mg, increases the surface area exposed so more collisions occur which leads to a faster rate.

When magnesium ribbon reacted with excess dilute hydrochloric acid at room temperature, the total volume of hydrogen produced was noted every 20 seconds.

The results obtained are given in the graph labeled C

drawn below

What was the final volume obtained in experiment C?

• 30 cm3

• 40 cm3

• 50 cm3

• 60 cm3

Answer explanation

60 cm3

this is where the curve flattens as the reaction stops and no more gas is produced so there is no increase in the volume of gas on the graph.

The graph below shows the volume of oxygen formed during the decomposition of 50 cm3

of hydrogen peroxide solution using 1 g of the catalyst.

Give one possible reason why the point (X) at 15 seconds is not on the graph line.

• Intentional to show variety in methods

• Experimental error

• should be placed at the beginning of the experiment

• Due to the use of large amount of catalyst

The graph below shows the volume of oxygen formed during the decomposition of 50 cm3

of hydrogen peroxide solution using 1 g of the catalyst.

What volume of oxygen is collected after 20 seconds?

• 30 cm3

• 40 cm3

• 50 cm3

• 60 cm3

The graph below shows the volume of oxygen formed during the decomposition of 50 cm3

of hydrogen peroxide solution using 1 g of the catalyst.

How long does it take to collect 40 cm3

of oxygen?

• 22 seconds

• 30 seconds

• 32 seconds

• 40 seconds

The graph below shows the volume of oxygen formed during the decomposition of 50 cm³

of hydrogen peroxide solution using 1 g of the catalyst.

When the reaction stopped, 1 g of the catalyst was still left.

What caused the reaction to stop?

• The catalyst was not enough

• All the hydrogen peroxide decomposed completely.

• 1 g of catalyst requires at least 100 cm³ of H₂O₂

• All the hydrogen peroxide decomposed the catalyst so temperature increased