Unit 6: The Rate and Extent of Chemical Change

Rate of Reaction

Calculating rate

quantity of reactant used/ time

Factors that affect rate of reaction

Units are cm^3 / second, g/s, mol/second

Temperature

Concentration

Surface area

Pressure (ONLY GASES)

INCLUDE MORE FREQUENT SUCCESFUL COLLISIONS IN EVERY ANSWER

If the pressure of a gas is increased, the particles are forced closer together causing more frequent successful collisions

If the concentration of a solution is increased, there are more particles in a given volume, increasing the rate by causing more frequent successful collisions

Increasing the temperature increases the Ke of the particles. Thus more particles have energy equal or greater than the activation energy therefore an increase in frequency of successful collisions thus higher rate of reaction.

Small pieces have a larger surface area than big chunks. Larger surface area means that there are more particles available to react so more frequent successful collisions occur.

Catalyst

A catalyst speeds up a reaction without changing itself. Catalysts work by lowering the activation energy needed by providing an alternate pathway for the reaction. Raj's Matchmaker analogy

Extent of Reaction

Effect of Changing Concentration

Increased concentration of reactant

Decreased concentration of reactant

Increased concentration of product

Decreased concentration of product

According to Le Chatelier's principle, the system acts to oppose the decrease in concentration. And so, the position fo the equilibrium shifts to the right-hand side to replace the lost products. Thus, an increase in yield of products

According to Le Chatelier's principle, the system acts to oppose the decrease in concentration. And so, the position of equilibrium shifts to the left-hand side to replace lost reactants.

According to Le Chatelier's principle, the system acts to oppose the increase of concentration. And so, the position of equilibrium shift to the left hand side to use up excess products.

According to Le Chatelier's principle, the system acts to oppose the increase the concentration. And so, the position of the equilibrium shifts to the right-hand side to use up excess reactiants. Thus, an increase in product yield.

Effect of changing temperature

Forward reaction is exothermic

Forward reaction is endothermic

Increase in temperature

Increase in temperature

Decrease in temperature

Decrease in temperature

Equilibrium shifts to oppose the increase the temperature. Reaction that absorbs extra heat is favoured (endothermic). Equilibrium shifts to the right-hand side. Thus, an increase in product yield

Equilibrium shifts to oppose the decrease in temperature . Reaction that gives out extra heat is favoured (exothermic). Equilibrium shifts to the left-hand side.

Equilibrium shifts to oppose the increase in temperature. Reaction that absorbs extra heat is favoured (Endothermic) Equilibrium shifts to the left hand side.

Equilibrium shifts to oppose the decrease in temperature. Reaction that gives out more heat is favoured (exothermic). Equilibrium shifts to the right-hand side. Thus, an increase in product yield.

Effect on Changing Pressure

More gas molecules of reactants

Same number of gas molecules on both sides

More gas molecules of product

Increase in pressure

Decrease in pressure

Equilibrium shifts to oppose the increase in pressure. Reaction that produces less moles of gas is favoured to reduce the pressure. Equilibrium shifts to the right hand side. Thus, an increase in product yield.

Equilibrium shifts to oppose the decrease in pressure. Reaction that produces the most moles of gas is favoured to increase the pressure. Equilibrium shifts to the left-hand side.

Position of Equilibrium does not change

Increase in pressure

Decrease in pressure

Equilibrium shifts to oppose the increase in pressure. Reaction that produces the least moles of gas is favoured to reduce the pressure. Equilibrium shifts to the left-hand side

Equilibrium shifts to oppose the decrease in pressure. Reaction that produces the most gas molecules is favoured to increase the pressure. Equilibirum shifts to the right-hand side. Thus, an increase in product yield.