Rates of Reaction

 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

 Increasing Temperature means the particles have more energy so are moving faster  Increasing rate of reaction

 Smaller particles = larger surface area  Increases the rate of reaction

 Increased concentration more particles in same space so faster rate of reaction

 Speed up a chemical reaction  Are not used up by the reactions

 Increasing the concentration  Increasing the temperature  Decreasing the particle size ◦ Which increases the surface area  Adding a catalyst

3. Magnesium reacts with hydrochloric acid. In which of the following experiments wouldthe reaction rate be fastest? 1 A. B. C. D. A 2009

 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.

BALANCE 50 cm 3 of 2 mol/l HCl + 10g marble chips Cotton wool plug Does the mass increase or decrease?? Why???

Collecting gases Under water Suitable for insoluble gases only eg carbon dioxide, methane, hydrogen & oxygen Gas collects water Delivery tube reactants

Gas Syringe – must be used for soluble gases eg sulphur dioxide & ammonia syringe reactants gas collects pushing plunger out

 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

2. Hydrogen peroxide solution decomposes to give water and oxygen Calculate the average rate of reaction between 0 and 20 seconds.

WATCH OUT WHERE DOES GRAPH START??

Steeper the slope, faster the reaction Reaction over – graph levels off Time/s Vol of gas/cm 3

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

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

Draw a line on graph to represent experiment B

2004 C