3.2 Rates of ReactionEdexcel IGCSE Chemistry: Flashcards

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How can the rate of a gas-producing reaction be measured experimentally?

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How can the rate of a gas-producing reaction be measured experimentally?: By measuring the volume of gas produced over time using a gas syringe, or by measuring the loss in mass of the reaction flask over time.
How does increasing surface area affect rate of reaction?: It increases the rate, because more particles are exposed and available to collide.
How does increasing concentration affect rate of reaction?: It increases the rate, because particles are closer together, increasing collision frequency.
How does increasing temperature affect rate of reaction?: It increases the rate, because particles collide more frequently and a greater proportion of collisions have energy exceeding the activation energy.
State collision theory.: Particles must collide with energy greater than or equal to the activation energy, and in the correct orientation, for a reaction to occur.
Define activation energy.: The minimum energy that colliding particles need for a reaction to occur.
Define a catalyst.: A substance that increases the rate of a reaction but is chemically unchanged at the end.
How does a catalyst increase the rate of reaction?: By providing an alternative reaction pathway with a lower activation energy.
On a reaction profile diagram, what does adding a catalyst change?: It lowers the activation energy hump; the overall energy change (ΔH) stays the same.
Describe an experiment to investigate how surface area affects the rate of reaction between marble chips and hydrochloric acid.: React marble chips of different surface areas (e.g. powder vs lumps) with the same volume/concentration of acid, measuring the volume of gas produced over time for each and comparing rates.
Describe an experiment to investigate solids as catalysts for hydrogen peroxide decomposition.: Add different solid catalysts (e.g. manganese(IV) oxide) separately to equal volumes/concentrations of hydrogen peroxide and compare the rate of oxygen gas production.
How does increasing the pressure of a gas affect rate of reaction?: It increases the rate, because gas particles are pushed closer together, increasing collision frequency.