C8 - Rates and Equilibrium

Question 1

Method for disappearing cross experiment

Answer 1

• Use a measuring cylinder to add 10cm3 of sodium thiosulfate to a conical flask
• Place flask onto a printed black cross
• Add 10cm3 of HCl
• Swirl the solution and immdiately start the timer
• Stop the timer once it has gone cloudy (due to sulfur) and you can no longer see the cross
• repeat to find a mean
• repeat with different concentrations of sodium thiosulfate

Question 2

Method for volume of gas produced by a reaction experiment

Answer 2

• Use a measuring cylinder to add 50cm3 HCl to a conical flask
• Attach a bung and delivery tube into a trough of water and and upturned measuring cylinder filled with water
• Add 3cm Mg ribbon
• Swirl + immediately start the timer once the bung is on
• Every 10s, measure the volume of gas collected until it is full
• Repeat to find a mean
• Repeat with different conc. HCl
• Control temperature, length of Mg and volume of HCl
• To find the rate, you do 1/time

Question 3

What is a reversible reaction?

Answer 3

Where products can react together to form the reactants. There is both a forward, and reverse reaction that can occur

Question 4

What is dynamic equilibria

Answer 4

where the forward reaction happens at the same rate as the reverse reaction. The concentration of reactants and products remains unchanged

Question 5

Define the activation energy

Answer 5

• The minimum amount of energy that particles have to collide with for there to be a reaction (successful collision)