Rates of ReactionEdexcel GCSE Chemistry: Flashcards

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Name a practical method for measuring the rate of the reaction between hydrochloric acid and marble chips.

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Name a practical method for measuring the rate of the reaction between hydrochloric acid and marble chips.: Measuring the volume of gas (CO2) produced over time, e.g. with a gas syringe.
Name a practical method for measuring the rate of the reaction between sodium thiosulfate and hydrochloric acid.: Timing how long it takes for a cross viewed under the flask to disappear as a cloudy precipitate of sulfur forms.
State collision theory.: Reactions only occur when particles collide with sufficient energy (at least the activation energy).
How does increasing temperature affect rate, and why?: It increases rate because particles move faster, colliding more frequently AND with more energy.
How does increasing concentration affect rate, and why?: It increases rate because there are more particles in the same volume, so collisions happen more frequently.
How does increasing surface area to volume ratio of a solid affect rate, and why?: It increases rate because more particles are exposed at the surface, so collisions happen more frequently.
How does increasing pressure affect the rate of a gas reaction, and why?: It increases rate because particles are pushed closer together, so collisions happen more frequently.
What does a catalyst do to the rate of a reaction?: It speeds up the rate without being used up or changing the products.
How does a catalyst increase the rate of a reaction?: It provides an alternative reaction pathway with a lower activation energy.
What is an enzyme?: A biological catalyst, e.g. those in yeast used to produce alcoholic drinks.
On a graph of product volume against time, what does a steeper initial gradient mean?: A faster rate of reaction.
On a graph of product volume against time, why does the line flatten out?: Because the reaction has finished — a reactant has been used up.