A student investigated the rate of decomposition of a hydrogen peroxide (H₂O₂) solution using manganese dioxide (MnO₂) as a catalyst - Leaving Cert Chemistry - Question 3 - 2018

The manganese dioxide (MnO₂) catalyst appears as a black solid or powder. It is generally dark in color and may have a granular texture when viewed under normal laboratory conditions.

To complete the diagram, you should include:

(i) The location of the catalyst just before the reaction is started by labeling it as 'catalyst' inside the flask labeled A. (ii) Show the arrangement of flexible tubing leading from the flask to a gas syringe labeled Y, which is used to collect the oxygen gas evolved during the reaction. Make sure to indicate that the gas syringe is inverted over water to measure the volume of gas accurately.

The graph should show the volume of oxygen (in cm³) on the y-axis against time (in minutes) on the x-axis. Each data point from the provided table should be accurately plotted. The axes must be labeled with their respective units. The plotted points should then be connected smoothly, forming a curve that gradually flattens as time progresses.

The rate of reaction slows down because as the hydrogen peroxide is consumed, its concentration decreases. According to the principle of reaction rates, a lower concentration of reactants results in fewer collisions between reactant molecules, leading to a slower formation of products, in this case, oxygen gas.

By locating the 2.5-minute mark on the x-axis, you can trace upwards to the graph curve to find the corresponding volume of oxygen produced. This should give you a precise value as indicated by the curve.

You should sketch a new curve on the same graph that starts at the origin and rises but is less steep than the original curve, indicating that a smaller volume of hydrogen peroxide would produce oxygen more slowly. Ensure to label this new line appropriately.