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Published byMary Maxwell Modified over 9 years ago
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Rates of Reaction
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Familiar with factors which affect reaction rate ◦ Temperature ◦ Particle Size / surface area ◦ Concentration ◦ Catalyst Average Rate Calculation ◦ From Graph ◦ Table ◦ Data given in Question ◦ Units Interpretation of Rate Graphs ◦ What steepness of graph means ◦ Drawing how to monitor reaction progress
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Increasing Temperature means the particles have more energy so are moving faster Increasing rate of reaction
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Smaller particles = larger surface area Increases the rate of reaction
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Increased concentration more particles in same space so faster rate of reaction
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Speed up a chemical reaction Are not used up by the reactions
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Increasing the concentration Increasing the temperature Decreasing the particle size ◦ Which increases the surface area Adding a catalyst
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3. Magnesium reacts with hydrochloric acid. In which of the following experiments wouldthe reaction rate be fastest? 1 A. B. C. D. A 2009
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Can be measured by following ◦ Change in mass ◦ Change in volume Must use the initial and final readings for the average in the given time interval.
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BALANCE 50 cm 3 of 2 mol/l HCl + 10g marble chips Cotton wool plug Does the mass increase or decrease?? Why???
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Collecting gases Under water Suitable for insoluble gases only eg carbon dioxide, methane, hydrogen & oxygen Gas collects water Delivery tube reactants
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Gas Syringe – must be used for soluble gases eg sulphur dioxide & ammonia syringe reactants gas collects pushing plunger out
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Average rate we are measuring a change in volume or mass. ◦ cm 3 s -1 = Change in volume / time ◦ gs -1 = change in mass / time Change in y-axis / change in x – axis Formula in Data Book
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2. Hydrogen peroxide solution decomposes to give water and oxygen. 2007 Calculate the average rate of reaction between 0 and 20 seconds.
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WATCH OUT WHERE DOES GRAPH START??
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Steeper the slope, faster the reaction Reaction over – graph levels off Time/s Vol of gas/cm 3
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Slower than red Could be: lower concentration lower temp larger particles Faster than red Could be: more concentrated higher temp smaller particles catalyst present Time/s Vol of gas/cm 3 All produce same volume of gas
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Slope same gradient, so speed the same – concentration, temp and particle size the same Half volume of gas given off so only half quantity of reactants used Time/s Vol of gas/cm 3
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Draw a line on graph to represent experiment B
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2004 C
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