6.1.1 Calculating Rates of Reactions

What is the Rate of Reaction?

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The rate of a chemical reaction tells us how quickly the reaction happens. It measures how fast the reactants are used up or how quickly the products are formed during a reaction.

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Rates of reaction are important because they help us understand how efficient a reaction is, which is particularly useful in industrial processes

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Calculating Mean Rate of Reaction The mean rate of reaction can be calculated using one of two formulas:

Using Reactants $Mean Rate of Reaction = \frac{Amount of Reactant Used}{Time Taken}$
Using Products: $Mean Rate of Reaction = \frac{Amount of Product Formed}{Time Taken}$

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A higher rate indicates a faster reaction, while a lower rate suggests a slower reaction.

Units:

The amount of reactant used or product formed is usually measured in grams (g) or cubic centimetres (cm³).
Time is measured in seconds (s).
Therefore, the rate is expressed in units like g/s or cm³/s.

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Example Question: Calculating the Mean Rate of Reaction A chemical reaction between magnesium and hydrochloric acid produces hydrogen gas. During an experiment, 0.12 grams of magnesium were completely consumed in 45 seconds, producing 100 cm³ of hydrogen gas.

Tasks:

Calculate the mean rate of reaction using the amount of reactant (magnesium) consumed.
Calculate the mean rate of reaction using the amount of product (hydrogen gas) formed.
Determine which calculation indicates a higher rate of reaction and explain why. Given Data:

Amount of magnesium used = 0.12 g
Amount of hydrogen gas formed = 100 cm³
Time taken = 45 s Units:
Rate using magnesium: g/s
Rate using hydrogen gas: cm³/s

Answers

Rate using magnesium: 0.00267 g/s
Rate using hydrogen gas: 2.22 cm³/s
Higher rate of reaction: The rate using hydrogen gas (2.22 cm³/s) is higher because it reflects the volume of gas produced, which occurs more quickly and in greater quantity compared to the mass of magnesium consumed.

Calculating Rates of Reactions Simplified Revision Notes for GCSE Edexcel Chemistry

6.1.1 Calculating Rates of Reactions

What is the Rate of Reaction?

Units:

Answers

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