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To investigate the effect of concentration on a reaction rate, a student measured 100 cm³ of a 0.10 M solution of sodium thiosulfate into a conical flask, added 10 cm³ of 1.0 M hydrochloric acid, and then placed the flask on top of a cross on a sheet of white paper as shown in the diagram - Leaving Cert Chemistry - Question 3 - 2002
Question 3
To investigate the effect of concentration on a reaction rate, a student measured 100 cm³ of a 0.10 M solution of sodium thiosulfate into a conical flask, added 10 c... show full transcript
Worked Solution & Example Answer:To investigate the effect of concentration on a reaction rate, a student measured 100 cm³ of a 0.10 M solution of sodium thiosulfate into a conical flask, added 10 cm³ of 1.0 M hydrochloric acid, and then placed the flask on top of a cross on a sheet of white paper as shown in the diagram - Leaving Cert Chemistry - Question 3 - 2002
Step 1
Step 2
Describe the procedure for preparing the 0.08 M solution of sodium thiosulfate from the 0.10 M solution.
Answer
To prepare the 0.08 M solution of sodium thiosulfate, use a graduated pipette to measure 80 cm³ of the 0.10 M sodium thiosulfate solution and place it into a volumetric flask. Then, add deionised distilled water until the total volume reaches 100 cm³.
Step 3
Plot a graph to show the relationship between the initial rate of this reaction and the concentration of sodium thiosulfate.
Answer
On the graph, plot the concentration of sodium thiosulfate (M) on the x-axis and the rate (1/time in min⁻¹) on the y-axis. Ensure that both axes are correctly labeled and data points are accurately plotted. Draw a straight line that passes through the origin.
Step 4
Use the graph to determine how long it would take for the cross on the sheet of paper to become obscured if the concentration of the sodium thiosulfate solution was 0.05 M.
Answer
From the graph, identify the rate corresponding to a 0.05 M sodium thiosulfate concentration. If the rate determined is, for example, 0.4 min⁻¹, then the time taken can be calculated as:
Step 5
Explain the relationship between the reciprocal of the time (1/time) and the initial rate of the reaction.
Answer
The reciprocal of the time (1/time) is directly related to the initial rate of the reaction. As the concentration of sodium thiosulfate increases, the time taken for the cross to become obscured decreases, resulting in a higher value for 1/time. This indicates that higher concentrations lead to faster reaction rates.