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Define rate of reaction - Leaving Cert Chemistry - Question 9 - 2012
Question 9
Define rate of reaction. The loss of mass of a mixture of 50 cm³ of a 2 M solution of hydrochloric acid and excess marble chips was monitored over time and the foll... show full transcript
Worked Solution & Example Answer:Define rate of reaction - Leaving Cert Chemistry - Question 9 - 2012
Step 1
Step 2
Plot a graph to show the mass of carbon dioxide produced (loss of mass) versus time.
Answer
- Label the x-axis as 'Time (s)' and the y-axis as 'Loss of mass (g)'.
- Scale the axes appropriately to accommodate the data.
- Plot the points based on the provided data:
- (0, 0.00)
- (20, 0.10)
- (40, 0.18)
- (80, 0.29)
- (120, 0.35)
- (160, 0.39)
- (240, 0.41)
- Draw a curve that accurately represents the trend of the data starting from the origin.
Step 3
Use your graph to find the instantaneous rate of the reaction at 60 seconds in g/s carbon dioxide produced.
Answer
To find the instantaneous rate at 60 seconds:
- Locate 60 seconds on the time axis.
- Draw a tangent to the curve at this point.
- Determine the slope of the tangent line to find the rate, which is the change in mass over the change in time.
Step 4
Mark clearly on your graph the curve you would expect to obtain if the reaction were repeated using 50 cm³ of a 1 M solution of hydrochloric acid.
Answer
- Draw a second curve on the same graph to indicate the expected results with a 1 M solution.
- This curve should start at the same point but rise to half the height achieved with the 2 M solution more quickly, then level off earlier, reflecting the lower concentration of HCl used.
Step 5
Justify the shape and position of this curve relative to the graph you have plotted.
Answer
The curve for the 1 M solution will rise less steeply at the start due to the lower concentration of HCl. Additionally, it will reach a maximum mass lower than the 2 M graph and will rise to half the height of the 2 M curve, as the reaction rate is generally affected by the concentration of the reactants. It will also level off sooner, reflecting the difference in the amount of HCl present.