C8 Rates and Equilibrium

• How fast a reactant is used up • How fast a product is produced

change in mass (g) or volume (cm3)/ change in time

If mass - g/s If volume - cm3/s

straight line bit / whole graph - Take mass or volume and divide by time Curve - Draw a tangent that touches the curve in ONLY one point - mass or volume/ time of the straight line

• Temperature • SA:V ration • Concentration • Catalyst

• Steeper line • Larger gradient • Large rate (0.4g/s is faster than 0.2 g/s)

• Increasing frequency of collisions • Increasing energy of collisions • Lowering activation energy

• the minimum amount of energy • with which the particles must collide • for the reaction to take place

For higher SA: - There are more particles in contact with the reactants - Therefore higher frequency of collision - Means higher rate of reaction

Measure if the number if particles of a substance in a certain volume of solution (aqueous)

a measure of the number of particles of a substance in a certain volume of gas (gas)

Increased conc/pressure: - There are more particles in the same volume - There is a higher frequency of collisions - higher rate of reaction

Higher Temp • Increased energy with which the particles move • As they move faster the frequency of collision increase • As more particles have more energy more collide with more energy than the activation energy • More collisions are successful • Both increase rate of reaction

If a cube increases by a factor of 10 the SA:V decreases by a factor of 10

• Usually transition metals • They are very expensive but save money • as more energy would be used • can be reused for a long time until they become ‘poisened’ by impurities • better for the environment as CO2 is not released

• They provide an alternate reaction pathway with a lower activation energy • Higher proportion of reactants have enough energy • Frequency of effective collision increase

• Dissapearing Cross • Loss of Mass • Gas collection

• Put a printed cross on the bench with a conical flask on top of it • Combine sodium thiosulfate and hydrochloric acid - 10cm3 (or two products which create a pricipitate • Start stop watch • Record how long it takes for the cross to disapear

• Add reactants (which make a gas) to a conical flask • Weigh the entire thing • start clock (step 1-3 should all happen simultaneously) • Every 30s record the loss of mass

• Fill the trough and a measuring cylinder with water • Place measuring cylinder upside in trough • Place reactants (make gas) in a conical flask • Use a bung and a delivery tube inserted under the tube • Measure how much gas is produced every 30s

The reactants are clear and colourless but the products contain a solid (a precipitate) so the solution is cloudy

A reaction in which the products can form the original reactants

Changing its conditions: Ammonium chloride ->(heat) <- (cooling) ammonia + hydrogen chloride

• If a reaction is endothermic in one direction it is exothermic in the other • Same amount of energy is transferred in both direction (one + and one -) hydrated copper sulfate (blue) -> (endo) <- (exo) anhydrous copper sulfate (white) + water