# GCSE: OCR gateway: C3: Rate of reaction

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• C2: Rate of reaction
• Reaction rates
• How much of the product has been formed over a fixed period of time
• Reaction fast at start and then slows down as the reactants are used up
• Ways  of measuring rates of reaction
• g/s + g/min: when measuring the mass of a product formed
• g/s for fast reactions
• g/min for slow reactions
• cm3/s + cm3/min when measure the volume of gas produced
• cm3/s for fast reactions
• cm3/min for slower reactions
• Calculating the rate of reaction
• Worked out with graph gradient
• Choose part of the graph where there's a straight line
• Measure the value of y and x
• Divid y by x
• Limiting reactants
• Reactant not in excess and used up at end of reaction
• Directly proportional to amount of product formed
• Reactions occur when particals collide together
• If no of reacting particals of one reactant is limited the no of collisions of particals by that reactant are limited
• Rate of reaction
• Reaction has finished
• Graph: horizontal line
• Table: numbers stop changing
• Faster reaction
• Graph: steepest line
• Table: larger change in readings
• Reacting partical model
• Chemical reactions occur when particals collide
• Rate of reaction = collisions per second with reacting particals
• Rate of reaction increase
• Temperature: Particals gain more kinetic energy and move around more quickly so there are more collisions per second
• Pressure: particals closer together so more collisions per second
• Concentration: particals more crowded so more collisions of reacting particals
• For a successful collision each particals must have enough energy to react