the rate and extent of chemical change Flashcards
what is activation energy?
the minimum amount of energy needed for a successful collusion
why does increasing the concentration speed up a reaction?
increasing the concentration increases the chance/frequency of successful collusions because there are more particles per unit volume
why does increasing temperature speed up a reaction?
increasing the temperature increases the chance/frequency of successful collusions because more particles have an energy greater than or equal to activation energy
why does increasing the surface area speed up a reaction?
increasing the surface area increases the chance/frequency of successful collusions because there are more sites for a reaction to take place.
explain how a catalyst speeds up a reaction?
catalysts speed up a reaction by providing an alternative pathway with lower activation energy without itself being used up
what does equilibrium mean?
when the rate of the forward reaction equals the rate of the backward reaction in a closed system
the forward reaction is…
exothermic
the backward reaction is…
endothermic
anhydrous copper chloride can be used to text for the presence of water what is a positive result?
a colour change from blue to pink
what happens to the yield of a reaction if temperature is increased?
increasing the temperature will favour the backwards endothermic reaction because the position of the equilibria will shift to oppose the change and the yield of the reaction will decrease
what happens to the yield of a reaction if pressure is increased?
increasing the pressure will favour the (backwards/forward) reaction with less molecules because the position of equilibria will shift to oppose the change and the yield of the reaction will increase
what happens to the yield of a reaction if concentration is increased?
increasing the concentration will favour the forward reaction to use up the extra (chemical name),the position of the equilibria will shift to oppose the change and the yield of the reaction will increase
what happens to the yield of a reaction if the temperature decreases?
decreasing the temperature will favour the forward exothermic reaction because the position of the equilibria will shift to oppose the change and the yield of the reaction will increase
what type of elements are usually catalysts? give an example
transition metals e.g. iron (Fe) or nickel(Ni)
how to calculate average rate of reaction(no graph)?
volume of gas produced/time taken
what two practicals can you use to see the effect of concentration on the rate of reaction?
gas collection by water displacement
gas syringe method
give steps 1-3 of the gas collection by water displacement required practical
1.use a measuring cylinder to pour 50cm of 1 mol/dm cubed of hydrochloric acid into a conical flask
2.attach the conical flask to a bung and delivery tube
3.now place the delivery tube into a container filled with water
give steps 4-5 of the gas collection by water displacement required practical
4.then place an upturned measuring cylinder which is also filled with water over the delivery tube
5.add a 3cm strip of magnesium to the hydrochloric acid and start a stopwatch-this should produce hydrogen gas in the measuring cylinder
give steps 6-8 of the gas collection by water displacement required practical
6.every 20 seconds measure the volume of hydrogen gas in the measuring cylinder
7.continue this until no more gas in given off
8.repeat the experiment using different concentrations of hydrochloric acid
what is a reversible reaction?
a chemical reaction that can proceed in both the forward and reverse directions,meaning the products can react back into the original reactants
