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| Question | Answer |
|---|---|
| What does the rate of a chemical reaction describe? | it describes how fast reactants turn into products |
| What are the two ways of finding out the rate of a chemical reaction? |
• how fast reactants are used up as they are made into products • how quickly the products of a reaction are made |
| Name three techniques to measure the rate of reaction. |
• measuring the decreasing mass of a reaction mixture • measuring the increasing volume of gas given off • measuring the decreasing light passing through a solution |
| When can you measure the rate of a reaction by using a change in mass? | when the reaction gives off a gas |
| How do you measure the rate of a reaction using decreasing mass? |
• place the reaction in a conical flask • place the flask on a top-pan balance • measure and record the mass at regular time intervals • plot mass of the reacting mixture against time • use the graph to work out the rate of reaction |
| How is the rate of reaction determined by using the graph of mass versus time? |
• the gradient of the graph at any given time is the rate of reaction at that time • draw a tangent to the graph • work out the gradient of the tangent • the gradient is the rate of reaction |
| Give an example of a reaction where rate can be measured by using decreasing mass and why? |
• marble chips and dilute hydrochloric acid • the mass of the reacting mixture decreases because the reaction gives of carbon dioxide gas |
| What is the formula for the mean rate of reaction when measured by decreasing mass? |
\( \text {Mean Rate of Reaction} = \frac{\text {Quantity of Reactant Used}}{\text {time}} \) |
| When can you measure the rate of a reaction by using the volume of gas given off? | when the reaction produces a gas |
| How do you measure the rate of a reaction using increasing volume? |
• place the reaction in a conical flask • insert a bung attached to a gas syringe in the top of the flask • measure and record the volume on the gas syringe at regular time intervals • plot volume on the gas produced against time • use the graph to work out the rate of reaction |
| How is rate of reaction determined by using the graph of volume versus time? |
• the gradient of the graph at any given time is the rate of reaction at that time • draw a tangent to the graph • work out the gradient of the tangent • the gradient is the rate of reaction |
| Give an example of a reaction where rate can be measured by using decreasing mass and why? |
• marble chips and dilute hydrochloric acid • the reaction produces carbon dioxide gas |
| What is the formula for the mean rate of reaction when measured by increasing volume? |
\( \text {Mean Rate of Reaction} = \frac{\text {Quantity of Product Formed}}{\text {time}} \) |
| Write the word equation for the reaction of calcium carbonate (marble chips) with dilute hydrochloric acid. | hydrochloric acid + calcium carbonate → calcium chloride + water + carbon dioxide |
| Write the symbol equation for the reaction of calcium carbonate (marble chips) with dilute hydrochloric acid. | 2HCl(aq) + CaCO3(s) → CaCl2(aq) + H2O(l) + CO2(g) |
| When can you measure the rate of a reaction by using the descreasing light passing through a solution? | a reaction where the production of an insoluble solid (precipitate) makes the solution cloudy |
| How do you measure the rate of a reaction using decreasing light passing through a solution? |
• place the reaction in a conical flask • mark a large X on a sheet of paper • place the flask on the paper covering the large X • observe the fading X with time |
| Give an example of a reaction where rate can be measured by using decreasing mass and why? |
• adding sodium thiosulphate to hydrochloric acid • the solution turns cloudy because of the sulphur that is produced |
| Write the word equation for the reaction of sodium thiosulphate with hydrochloric acid. | sodium thiosulphate + hydrochloric acid → sodium chloride + water + sulphur dioxide + sulphur |
| Write the symbol equation for the reaction of sodium thiosulphate with hydrochloric acid. | Na2S2O3(aq) + 2HCl(aq) → 2NaCl(aq) + H2O(l) + SO2(g) + S(s) |
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