Rate of Reaction Flashcards
(10 cards)
Explain the method of the disappearing cross method.
Draw a black cross on a piece of paper and place a conical flask on top of it.
Add a fixed volume of sodium thiosulfate solution into the flask.
Add a fixed volume of dilute hydrochloric acid to the flask and immediately start the stopwatch.
Look down through the solution and stop the timer when the black cross is no longer visible.
Repeat the experiment with different concentrations of sodium thiosulfate (or acid) to investigate the effect of concentration on the rate of reaction.
Keep all other variables the same for a fair test (e.g., temperature, volumes, depth of liquid).
Explain the method of measuring the rate of reaction with a gas syringe.
Add a set volume of acid to a conical flask.
Connect a gas syringe to the flask using a bung and delivery tube.
Add a set mass of a solid reactant (e.g., magnesium or marble chips), quickly seal the flask with the bung, and start a stopwatch.
Record the volume of gas produced in the syringe at regular intervals (e.g., every 10 seconds).
Plot a graph of gas volume against time to compare rates.
Repeat the experiment using different concentrations of acid or different surface areas of the solid reactant.
Explain a reversible reaction.
A reversible reaction is a chemical reaction where the products can react to reform the original reactants.
Explain dynamic equilibrium.
Dynamic equilibrium occurs in a closed system when the forward and reverse reactions happen at the same rate, so the concentrations of reactants and products remain constant.
example of a reversible reaction
This reaction is reversible when heated and cooled.
Key points to remember in a dynamic equiblium
It only happens in reversible reactions in a closed system.
The reaction hasn’t stopped – particles continue to react, but the amounts of substances stay the same.
Changing conditions like temperature or pressure can shift the position of equilibrium.
Explain Le Chatelier’s Principle.
Le Chatelier’s Principle states that if the conditions of a system at equilibrium are changed, the system will shift to oppose the change and try to restore equilibrium.
what happens when you increase temperature (LCP)
Increase temperature → equilibrium shifts in the endothermic direction.
what happens when you increase pressure (LCP)
Increase pressure → equilibrium shifts to the side with fewer gas molecules.
what happens when you increase concentration of a reactant (LCP)
Increase concentration of a reactant → equilibrium shifts to the right to use it up.
