Why does a higher concentration increase the rate?

More particles in the same volume, so more frequent collisions.

Why does increasing pressure increase the rate of a gas reaction?

The gas particles are closer together, so they collide more frequently.

Why does a higher temperature increase the rate?

Particles move faster so collide more often, and more collisions have enough energy to react.

What is the effect of breaking a solid into smaller pieces?

Larger surface area, more frequent collisions and a faster rate.

A substance that speeds up a reaction and is not used up.

How does a catalyst work?

It provides an alternative route with a lower activation energy.

If the same mass of reactant is used, how do final volumes compare for fast and slow reactions?

They are the same; only the time taken is different.

Is surface area the same as size?

No; smaller pieces have a larger surface area for the same mass.

Factors affecting rateIB MYP Chemistry: Flashcards

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Question

Name five factors that affect the rate of reaction.

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Name five factors that affect the rate of reaction.: Concentration, temperature, surface area, pressure (gases) and catalysts.
Why does a higher concentration increase the rate?: More particles in the same volume, so more frequent collisions.
Why does increasing pressure increase the rate of a gas reaction?: The gas particles are closer together, so they collide more frequently.
Which factor affects only reactions involving gases?: Pressure.
Why does a higher temperature increase the rate?: Particles move faster so collide more often, and more collisions have enough energy to react.
What is the effect of breaking a solid into smaller pieces?: Larger surface area, more frequent collisions and a faster rate.
What is a catalyst?: A substance that speeds up a reaction and is not used up.
How does a catalyst work?: It provides an alternative route with a lower activation energy.
Name the catalyst used in the Haber process.: Iron.
What shape is the line for a faster reaction on a volume against time graph?: Steeper, levelling off sooner.
If the same mass of reactant is used, how do final volumes compare for fast and slow reactions?: They are the same; only the time taken is different.
Roughly how does a 10 °C rise change the rate of many reactions?: It roughly doubles it.
Is surface area the same as size?: No; smaller pieces have a larger surface area for the same mass.

Exam questions on Factors affecting rate

A student in Lima reacts 1.0 g of zinc granules with 50 cm³ of excess dilute hydrochloric acid and measures the volume of hydrogen made over time. She then repeats the experiment with 1.0 g of zinc powder, keeping everything else the same.
Explain why zinc powder reacts faster than zinc granules.2 marks
Ammonia for fertiliser is made in the Haber process, in which nitrogen gas reacts with hydrogen gas at high temperature and high pressure in the presence of an iron catalyst. Engineers at the plant are always looking for ways to make ammonia faster.
State two ways, other than adding a catalyst, of increasing the rate of the reaction between nitrogen and hydrogen.2 marks
An engineer in Seoul tests an effervescent tablet that fizzes when it is dropped into 200 cm³ of water. She times how long the tablet takes to stop fizzing at three temperatures. At 15 °C it takes 120 s, at 25 °C it takes 60 s and at 35 °C it takes 30 s.
Describe the effect of temperature on the rate of reaction, using the data to support your answer.3 marks

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Written by the Exaim team, led by Shaun Daswani (Head of Upper Secondary, Improve ME Institute; MSc Financial Mathematics, Imperial College London; BSc, UCL) and Jason Daswani (operational lead, Improve ME Institute; LSE).