Name _________________________
Date __________Section__________
Lab #14 Determining the Rate of a Reaction
Introduction: When atoms or molecules collide with enough energy and with the proper
orientation an effective reaction can occur. Today we will be testing how the concentration of a
reactant affects the speed or “rate” of a reaction. We will be using a 2.0 mol/L hydrochloric acid
(HCl) solution that can seriously burn your eyes and skin. All students must wear gloves
and goggles during the entire lab. You must also work safely and slowly and remain in
your seat at all times. Only the material manager is permitted to get out of their seat to get and
return equipment and materials. Students disobeying the teacher’s instructions will lose their
participation points for the entire week. Continuing to disobey the teacher will result in Saturday
Detention.
AIM: How does concentration of a reactant affect the reaction rate?
Pre-Lab Questions:
1. What is an aqueous solution?
2. How many moles of Na2S2O3 are in 1 L of solution with a concentration of 0.20 M?
3. Define the collision theory.
Materials: To be obtained and returned by the material manager.
50 mL graduated cylinder (for measuring Na2S2O3 and tap water)
10 mL graduated cylinder (for measuring HCL)
250-mL beaker
Sheet of white paper
0.20 M Na2S2O3
Black marking pen
2.0 M HCl
Stopwatch
Tap water
Name _________________________
Date __________Section__________
Procedure: To be read by the information specialist and performed by the experimentalist.
1.
Use the 50 mL graduated cylinder to measure and add 0.20 M Na2S2O3 and tap water to the
beaker as described below in #1:
Beaker
Test #1
Test #2
Test #3
Test #4
Test #5
Na2S2O3
10.0 mL
20.0 mL
30.0 mL
40.0 mL
50.0 mL
Water
40.0 mL
30.0 mL
20.0 mL
10.0 mL
0.0 mL
2. Use the pipet in the flask of hydrochloric acid to measure out 5 mL of HCl into the 10 mL
graduated cylinder. BE CAREFUL AND REPORT ANY SPILLS TO THE TEACHER!!
3. On a sheet of paper, use the marking pen to write the letter X small enough so that it can be
covered by the beaker.
4. Place the beaker on the X. Use the graduated cylinder to add 5.0 mL of 2.0 mL HCl to the
beaker. Start the stopwatch when the HCl is added. Immediately give the beaker on gentle 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.
5. Gently rinse the solution in the beaker down the drain being careful not to splash the liquid
anywhere.
6. Repeat the procedure for Test #2, #3, #4, #5.
Data Table 1:
Beaker Test #
1
2
3
4
5
Volume of Na2S2O3
(mL)
Volume of Water
(mL)
Volume HCl (mL)
Reaction Time (sec)
Name _________________________
Date __________Section__________
Pre-Lab Questions:
1. What visible indication is there that a chemical reaction is occurring?
2. Prepare a line graph of time versus volume of Na2S2O3
3. Calculate how many moles of Na2S2O3 are in 50 mL of the 0.2 M solution?
Show your work!
.
Critical Thinking
1. How did the concentration of Na2S2O3 affect the rate of the reaction?
**Be specific and write about the evidence contained in the data table and the line graph
to support your observations and explanations.