STOICHIOMETRY LAB:
LIMITING REAGENT WITH ACID AND BASE
Names: _____________________
Partner group:________________
Introduction:
The reactions carried out in this lab will be acid-base reactions. The equations are:
HCl + NaOH  NaCl + H2O
H2SO4 + NaOH  Na2SO4 + H2O
In this lab you will experiment with the concept of a limiting reactant. You have two acids, labeled A and
B. One is hydrochloric acid (HCl) and the other is sulfuric acid (H2SO4). The main goal is to determine
which acid is which. When an acid and a base react, heat is given off. Therefore, you can get an idea of
the extent of a reaction by measuring the temperature change. That is, the greater the temperature change,
the more produce is formed.
After you have done your calculations answer this question; which trials would you expect to see the
greatest temperature change?
Pre lab Preparation:
Write the balanced equations here:
Define limiting reagent:
Given the data below calculate whether the acid or the base is the limiting reagent.
You must show ALL your calculations on a separate sheet.
Trial Moles Moles
Limiting
Trial Moles Moles
Limiting
#
HCl
NaOH
Reagent?
#
H2SO4 NaOH
Reagent?
1
0.040 0.010
1
0.040 0.010
2
0.035
0.015
2
0.035
0.015
3
0.030
0.020
3
0.030
0.020
4
0.025
0.025
4
0.025
0.025
5
0.020
0.030
5
0.020
0.030
6
0.015
0.035
6
0.015
0.035
7
0.010
0.040
7
0.010
0.040
How did you know which reagent was the limiting reagent?
Given the data above, predict what a graph of the change in temperature (y axis) vs moles of NaOH (x
axis) would look like for each acid. Draw one graph and make sure to label it appropriately. Then draw
the general shape of each acid on the graph, use a different color for each acid.
STOICHIOMETRY LAB:
LIMITING REAGENT WITH ACID AND BASE
Name: _____________________
Partner:______________________
Acid: ______________________
Introduction:
The reactions carried out in this lab will be acid-base reactions. The unbalanced equations are:
HCl + NaOH  NaCl + H2O
H2SO4 + NaOH  Na2SO4 + H2O
In this lab you will experiment with the concept of a limiting reactant. You have two acids, labeled A and
B. One is hydrochloric acid (HCl) and the other is sulfuric acid (H2SO4). The main goal is to determine
which acid is which. When an acid and a base react, heat is given off. Therefore, you can get an idea of
the extent of a reaction by measuring the temperature change. That is, the greater the temperature change,
the more produce is formed.
After you have done your calculations answer this question; which trials would you expect to see the
greatest temperature change?
Pre lab Preparation:
Write the balanced equations here:
Define limiting reagent:
Given the data below calculate whether the acid or the base is the limiting reagent. You MUST show
ALL your calculations on another sheet):
Trial ml
#
HCl
1
40.0
Moles
HCl
ml
Moles
NaOH NaOH
10.0
2
35.0
15.0
3
30.0
20.0
4
25.0
25.0
5
20.0
30.0
6
15.0
35.0
7
10.0
40.0
Limiting
Reagent?
How did you know which reagent was the limiting reagent?
Each substance is 1.00 M. This means
that there are 1.00 moles of substance
for every 1.00 L of liquid.
To find how many moles there are
divide the ml of substance to get liters
of substance. Then multiply the liters
by the molarity (M).
1𝐿
40.0 𝑚𝑙 𝐻𝐶𝑙 𝑥 (
)
1000 𝑚𝑙
= .04 𝐿 𝐻𝐶𝑙
1.00𝑚𝑜𝑙
)
𝐿
. 04 𝐿 𝑥 (
= .04 𝑚𝑜𝑙 𝐻𝐶𝑙
Trial ml
Moles
ml
Moles
Limiting
#
H2SO4
H2SO4
NaOH
NaOH
Reagent?
1
40.0
10.0
2
35.0
15.0
3
30.0
20.0
4
25.0
25.0
5
20.0
30.0
6
15.0
35.0
7
10.0
40.0
Given the data above, predict what a graph of the change in temperature (y axis) vs moles of NaOH (x
axis) would look like for each acid. Draw one graph and make sure to label it appropriately. Then draw
the general shape of the graph for each acid; use two different colors for the acids.
Procedure:
1. Measure out the appropriate amount of NaOH and take its temperature.
2. Measure out the appropriate amount of acid.
3. Pour the acid into the NaOH and stir.
4. Monitor the temperature and record the highest temperature reached. Be as precise as possible.
5. When you are finished taking the data, pour the solution down the drain.
6. Repeat steps 1-5 for each trial.
7. When you are finished with the lab, rinse your graduated cylinders, cups and beakers and put
them on the center table.
Unknown Acid ________
Trial #
1
mL
Acid
40.0
mL
Base
10.0
2
35.0
15.0
3
30.0
20.0
4
25.0
25.0
5
20.0
30.0
6
15.0
35.0
7
10.0
40.0
Initial Temp
Final Temp
Temp. Change
Analysis:
With your lab partner you will analyze your data. Make a visual display that answers the following
questions. You will present these to the class.
1. With your partner make a graph for this experiment. Follow the directions for the graph you made
in the prelab section, but plot the points as precisely as possible. You will need to share data with
another group so that you can plot both acids.
Trial #
Temp Change for
other Acid Unknown ______
1
2
3
4
5
6
7
2. Determine the identities of the unknowns A and B.
3. Explain how you knew which acid was which.
4. Explain why the graphs are different.