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GCSE2 rate reaction
AQA GCSE chapter 08 (part 1) rate of reaction
| Question | Answer |
|---|---|
| name 4 factors that can speed up a reaction | Hotter solution, More concentrated, Smaller bits, Catalyst (to merely say "heat" is not enough... read the question) |
| explain why a reaction goes faster when a solution is more concentrated | there are more particles IN THE SAME VOLUME, so there will be more FREQUENT collisions |
| explain why a reaction goes faster when a solution is hotter | Particles move FASTER, so the collisions have more energy, the collisions are more FREQUENT and more SUCCESSFUL |
| explain why a reaction goes faster when bits are smaller | there is a larger surface area exposed, so more particles can react so there are more FREQUENT collisions (for the same period of time) |
| what is a catalyst? | a chemical that speeds up the reaction without getting used up |
| explain how a catalyst speeds up a reaction | it lowers the activation energy and provides an alternative pathway |
| what is the activation energy | the minimum of energy required for the particles to collide and bonds to break |
| How do manufacturers of cars ensure that the catalytic converters convert the maximum possible of harmful gases into Carbon Dioxide and Water? | Increasing surface area (honeycomb structure); high temperature |
| In the catalytic converter, what are the harmful gases that need to be converted before coming out of the exhaust? | Carbon monoxide and Unburnt Hydrocarbons |
| An excess of Magnesium is reacted with a dilute solution of Acid. 40cm3 of Hydrogen is collected. The experiment is repeated at a hotter temperature. How much gas will be collected? More/less/same as (ie40cm3) | The same as: 40cm3; because you have the same amounts at the start in both experiments; so you collect the same at the end! |
| An excess of Magnesium is reacted with a dilute solution of Acid. 40cm3 of Hydrogen is collected. The experiment is repeated with a MORE CONCENTRATED acid. How much gas will be collected? More/less/same as (ie40cm3) | More than 40cm3; because there is more particles FOR THE SAME VOLUME in the concentrated acid so more gas particles will be collected |
| An excess of Magnesium is reacted with a dilute solution of Acid. 40cm3 of Hydrogen is collected. The experiment is repeated with a MORE CONCENTRATED acid.Would you expect the line at the start to be steeper/not as steep/same gradient? | More concentrated=faster; As the reaction is faster, the line will be steeper (more volume collected for the same time) |
| A student plots volume of gas collected against time for a given reaction. He repeats the experiment at a hotter temperature. Would you expect the line at the start to be steeper/not as steep/same gradient? | Hotter=faster; As the reaction is faster, the line will be steeper (more volume collected for the same time) |
| A student plots volume of gas collected against time for a given reaction. He repeats the experiment at a hotter temperature. Would you expect the line at the end to be higher/lower or at the same height as the first experiment? | same height because the same AMOUNT of chemicals was taken for both experiment |
| Predict what would happen to the rate of reaction if in the second experiment, you took double the volume of the same concentration, at the same temperature | Nothing! Volume does not affect the rate of reaction! |
| A students places Marble chippings in acid and observe the volume of gas collected. DESCRIBE the shape of the graph (volume on y-axis and time on x-axis) | Steep line at the start, the line is not so steep and at some stage the line goes HORIZONTAL (do not say flat) |
| A students places Marble chippings in acid and observe the volume of gas collected. EXPLAIN the graph (volume on y-axis and time on x-axis) will level out and have an horizontal line at the end | Steep line at the start because there are LOTS of particles in the same volume, as the reaction progresses there are less particles so slower reaction; eventually there are no particles, no gas is produced and the line goes HORIZONTAL |
| How do you work out the rate of reaction in the thio experiment where you observe how long it takes for the cross to disappear? | rate=1/time |
| On a graph volume of gas vs time, how would you work out the rate of reaction at time=0seconds? | Draw the tangent to the curve; draw a LONG tangent; then work out the gradient of the tangent; the gradient is the rate |
| How do you work out the gradient of a line? | gradient=rise over run; take points that are as far as possible |
Created by:
ursulinechem2
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