Determining Reaction Rate

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Objective To determine the relationship between concentration and reaction rate.

Lab Safety

Procedure Use graduated cylinders to measure 0.20 M Na2S2O3 (sodium thiosulfate) and distilled water to the beakers as described below: On a sheet of paper, use a pen to write the letter X small enough so that it can be covered by a beaker. Beaker 1 2 3 4 5 Na2S2O3 10.0 ml 20.0 ml 30.0 ml 40.0 ml 50.0 ml Water 0.0 ml

Procedure, con… Place beaker 1 on the X. Use the remaining graduated cylinder to add 5.0 ml of 2.0 M HCl to the beaker. Be careful to use proper safety precautions when working with acid. Record the time at which the HCl is added in the table below. Immediately give the beaker one gently swirl and place it back on the X. Look through the solution at the X and record the time at which the X is no longer visible. Repeat step 3-4 for the remaining beakers.

Data Beaker Volume of Na2S2O3 (ml) Reaction Time (seconds) 1/seconds 1   2 3 4 5

Observation Questions What visible indication is there that a chemical reaction is occurring? How is the concentration of Na2S2O3 affected by the volume of distilled water? What happens to the reaction time as the volume of distilled water increases relative to the volume of Na2S2O3? Using Excel, prepare a graph of time versus volume of Na2S2O3 by plotting time on the x axis and volume along the y axis. Using Excel, prepare a graph of 1/seconds versus volume of Na2S2O3 by plotting time on the x axis and volume along the y axis.

Analysis and Conclusion How did the concentration of Na2S2O3 affect the rate of the reaction? Does the graph support your conclusion for question 1? Explain.