A student investigated the rate of decomposition of hydrogen peroxide in the presence of a manganese(IV) oxide catalyst:
2H2O2(aq)→2H2O(l)+O2(g)2\text{H}_2\text{O}_2\text{(aq)} \rightarrow 2\text{H}_2\text{O(l)} + \text{O}_2\text{(g)}2H2O2(aq)→2H2O(l)+O2(g)
The volume of oxygen gas collected was measured over time. The student plotted a graph of the volume of oxygen gas collected in cm3\text{cm}^3cm3 against time in seconds, as shown below.
To determine the rate of reaction at t=50 st = 50\text{ s}t=50 s, a tangent was drawn to the curve at that point. The tangent line passes through the coordinates (15 s,14.5 cm3)(15\text{ s}, 14.5\text{ cm}^3)(15 s,14.5 cm3) and (95 s,48.1 cm3)(95\text{ s}, 48.1\text{ cm}^3)(95 s,48.1 cm3).
Calculate the rate of reaction at t=50 st = 50\text{ s}t=50 s. Give your answer to 2 significant figures and include the units.
Explain why the rate of reaction decreases and eventually becomes zero.