Question

some students investigated the rate of decomposition of hydrogen peroxide. the equation for the reaction is: hydrogen peroxide → water + oxygen. (a) complete the sentence. choose an answer from the box. a burning splint a glowing splint damp litmus paper limewater the students tested the gas produced to show that it was oxygen. (b) the method student a used did not give repeatable results. how could student a make the results repeatable? tick (✓) one box. student a should make measurements every 2 minutes. student a should measure the mass of manganese dioxide. student a should use 50 cm3 hydrogen peroxide. student a should use a beaker instead of a conical flask. (c) student b used a method which gave repeatable results. how could student b improve the accuracy of these results? tick (✓) one box. calculate a mean but do not include any anomalies. calculate a mean but do not include the first set of results. record the results in a table and plot the results on a bar chart. record the results in a table and plot the results on a line graph. (d) the figure below shows student bs results for coarse manganese dioxide lumps. calculate the mean rate of reaction between 30 and 250 seconds for coarse manganese dioxide lumps. use the figure and the equation: mean rate of reaction = volume of oxygen formed / time taken give your answer to 3 significant figures. volume of oxygen in cm3 time in s 0 0 10 100 20 200 30 300 40 400 50 500 60

Explanation:

Step1: Answer part (a)

Oxygen relights a glowing splint. So the answer is a glowing splint.

Step2: Answer part (b)

To make results repeatable, taking multiple measurements (repeats) and calculating a mean helps. Student A could take more measurements at regular intervals (e.g., every minute instead of every 2 minutes) and repeat the whole experiment multiple times.

Step3: Answer part (c)

To improve accuracy, Student B could use a more precise gas - measuring device (e.g., a gas syringe with smaller graduations), control the temperature and pressure more carefully during the experiment, and ensure proper mixing of reactants.

Step4: Answer part (d)

From the graph, at 30 s, the volume of oxygen is approximately 20 cm³ and at 250 s, it is approximately 90 cm³. The mean rate of reaction = $\frac{\text{Volume of oxygen formed}}{\text{Time taken}}=\frac{90 - 20}{250 - 30}=\frac{70}{220}\approx0.318$ cm³/s (to 3 significant figures)

Answer:

(a) a glowing splint
(b) Take more measurements at regular intervals and repeat the whole experiment multiple times.
(c) Use a more precise gas - measuring device, control temperature and pressure carefully, and ensure proper mixing of reactants.
(d) 0.318 cm³/s