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25 Cards in this Set
- Front
- Back
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3 ways to measure time taken for chemical reaction |
-loss in mass of reactants/time -volume of gas produced/time -time for solution to become opaque or coloured |
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Mean rate of reaction equations |
-quantity of reactant used/time -quantity of product formed/time |
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Factors that affect the rate of reaction |
-temperature -concentration of reactants -pressure of reacting gases -surface area of solid reactants -presence of catalysts |
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What happens when pressure is increased ? |
-reactant particles become more crowded -frequency of collisions between reactant particles increases -ROR increases |
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What happens when surface area is increased? |
-more reactant particles are exposed at the surface -the frequency of collisions between particles increases -ROR increases |
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What happens when temperature is increased? |
-reactant particles move quicker -energy of particles increases -frequency of successful collisions between particles increases -ROR INCREASES |
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Catalyst |
Substance that changes the rate of a chemical reaction. -provides an alternative reaction pathway that has a lower activation energy |
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Catalyst |
Substance that changes the rate of a chemical reaction but does not get used up. -provides an alternative reaction pathway that has a lower activation energy |
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Activation energy |
Minimum amount of energy that particles must have to react |
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What happens when concentration is increased? |
-Reactant particles become more crowded. -frequency of collisions between reactants particles increases -ROR INCREASES |
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Measuring effect of concentration on rate of reaction |
-measure 50cm^3 of dilute HCL -add 0.4g of calcium carbonate to the flask -immediately connect the gas syringe and start a stop clock -every 10 seconds, record the volume of gas produced. -repeat with different molar concentrations of HCL |
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Measuring rate of reaction by colour change |
-add 50cm^3 of dilute sodium thiosulfate solution to a conical flask -place conical flask on piece of paper with black cross drawn -add 10cm^3 of dilute hydrochloric acid to the conical flask. -mix its contents and start stop watch. -when cross can no longer be seen, record time -measure and record temperature of mixture -repeat using different starting temperatures of sodium thiosulfate solution |
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Reversible reaction example |
Ammonium chloride> |
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Exothermic |
Energy is given out to the surroundings |
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Endothermic |
Energy is taken in from the surroundings |
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Reversible reaction example (2) |
Hydrated copper sulfate>< anhydrous copper sulfate +water |
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Equilibrium |
When the forwards and backwards reactions happen at the same rate when the concentrations stay the same |
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Le chateliers principle |
If a system is at equilibrium and a change is made, then the system responds to counteract that change |
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If concentration of reactant is increased ? |
-more products will be formed until equilibrium is reached |
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If concentration of reactant is increased ? |
-more products will be formed until equilibrium is reached |
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If concentration of product is decreased? |
More reactants will react until equilibrium is reached again |
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If temperature increases? |
-amount of products at equilibrium increased for endothermic -amount of product at equilibrium decreases for exothermic |
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If temperature is decreased? |
-amount of product decreases in endothermic -amount of product increases in exothermic |
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If pressure is increased |
-equilibrium shifts to the side with fewer molecules |
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If pressure is decreased |
-equilibrium shifts towards the side with The larger number of molecules |
