chemistry - rate of reaction

Question 1

what are three ways of measuring the rate of a reaction?

Answer 1

• observe how quickly a precipitate forms
• measure the change in mass
• measure the volume of gas given off

Question 2

how to calculate the rate of reaction?

Answer 2

rate of reaction = amount of product formed or reactant used / time

Question 3

how can the rate of reaction be measured if a precipitate is produced?

Answer 3

• place piece of paper with a black cross below the reaction vessel and observe
• measure how long it takes for the cross to disappear

Question 4

How could you measure the rate of reaction if the coloured reactants forma colourless solution?

Answer 4

time how long it takes for the reactants to turn colourless

Question 5

why is the precipitate and colour change rate experiment not very reliable?

Answer 5

it is very subjective - people have different opinions over the exact point a mark disappears or the solution fully changes colour

Question 6

how can you find the rate of reaction of a reaction after a specified amount of time?

Answer 6

• plot results on a graph
• time along the x axis, and amount of product formed/reactant used on the y axis
• draw a tangent to the specified time point and calculate the gradient
  gradient = change in y / change in x

Question 7

what are the units rate of reaction when measuring a change in mass?

Answer 7

g/s

Question 8

what are the units of rate of reaction when measuring the volume of gas given off?

Answer 8

cm^3/s

Question 9

how can you investigate how HCl concentration affects the rate of reaction when magnesium is added?

Answer 9

• place the HCl in a conical flask
• add magnesium ribbon and quickly fit bung and gas syringe
• record volume of gas collected every 10 seconds
• repeat with a different concentration of HCl
• compare the rates of reaction

Question 10

how can you investigate how sodium thiosulfate concentration affects the rate of reaction when reacted with HCl?

Answer 10

• add 30cm^3 of sodium thiosulfate to a conical flask
• add 10cm^3 dilute HCl
• measure the time taken for the cross to disappear
• repeat three times for mean time
• repeat with different concentrations of sodium thiosulfate
• compare the times for each concentration