Rate of reaction

EasyMediumHard
123456789101112131415161718192021222324252627282930313233343536
Question 27
Medium

Yeast contains the enzyme catalase, which acts as a catalyst to speed up the decomposition of hydrogen peroxide solution into water and oxygen gas.

2H2O2(aq)→2H2O(l)+O2(g) \mathrm{2H_2O_2(aq) \rightarrow 2H_2O(l) + O_2(g)} 2H2​O2​(aq)→2H2​O(l)+O2​(g)

A student investigated the rate of this reaction using the following method:

  1. Add 40 cm340\text{ cm}^340 cm3 of 1.5 mol/dm31.5\text{ mol/dm}^31.5 mol/dm3 hydrogen peroxide solution to a conical flask.
  2. Add 5 cm35\text{ cm}^35 cm3 of yeast suspension to the flask.
  3. Immediately place the conical flask on a digital balance and start a timer.
  4. Record the total mass lost from the conical flask at regular intervals.
a.

Explain how the catalase catalyst increases the rate of decomposition of hydrogen peroxide.

[2]
b.

Explain why the mass of the conical flask and its contents decreased during the reaction.

[2]
c.

The graph below shows the results of this first investigation.

A graph showing 'Total mass lost in grams' on the y-axis against 'Time in seconds' on the x-axis. The y-axis scales from 0.00 to 1.20 in steps of 0.10. The x-axis scales from 0 to 120 in steps of 10. A curve starts at (0, 0), rises, and levels off horizontally at 1.00 g at approximately 80 seconds. A tangent to the curve is drawn at 50 seconds. This tangent line passes through the coordinates (10 s, 0.38 g) and (90 s, 0.98 g).

Determine the rate of reaction when the time was 505050 seconds. Give your answer to 2 significant figures. Show your working.

[4]
d.

The student repeated the investigation using 40 cm340\text{ cm}^340 cm3 of 0.75 mol/dm30.75\text{ mol/dm}^30.75 mol/dm3 hydrogen peroxide solution with the same volume of yeast suspension.

Describe two key features of the curve you would expect to see for these new results compared to the original curve.

[2]

Rate of reaction Questions

  1. GCSE
  2. /Chemistry
  3. /Rate of reaction