This experiment investigates how the concentration of hydrochloric acid (HCl) affects the conductivity when zinc is added. Five trials were conducted with varying molar concentrations of HCl (4M, 2M, 1M, 0.5M, and 0.25M) and the conductivity was measured over time. The results show that conductivity decreases more slowly at lower HCl concentrations. Specifically, the conductivity rate decreases from 2.532 μS/cm/s for 4M HCl to 3.425 μS/cm/s for 0.25M HCl. Thus, lower HCl concentrations lead to smaller decreases in conductivity over time when zinc is added.

1. Conductivity Rate
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2. Background information
-Conductivity is a gross, indirect measurement of the concentration of ions present in a liquid
solution. The purpose of this experiment is to observe the relationship between the concentration
in the molar of HCl and the conductivity rate. In this experiment, 2g of Zinc will be added to
different molar of HCl and it will be constant. The change that we observe will between thirty
second. There will be five data point and each will have five different decrease or increase
conductivity. Each data point will be presented graphically to see their relationship.
Materials
1. 5-250ml beaker
2. Conductivity Probe
3. Water
4. HCl
5. Zn
6. Timer
7. Goggle
8. Balance
9. Calculator
10. Cylinder
11. Stamp
Safety
Goggle on
Do not touch the reaction
No Food
Wash hand after done
Design
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3. 1. How does the change in concentration of HCl affect the conductivity in adding Zinc.
2HCl + Zn ------ H2 + ZnCl2
Independent Variable: Pressure
Dependent Variables: conductivity, time
Controlled Variable: Temperature(degree), Mass(g), HCl
2. Pressure: In this experiment, pressure is totally independent.
Time: You will observe how the reaction rate changes in every 30 second.The time will
stop at 180s.
Mass(Zn): You must weigh the mass of Zinc. It mass be 2g for each data point.
Conductivity: This is the most vital part; you need to record the conductivity data on
your table.
Temperature: Temperature is the one variable that you want to keep constant as possible
as you can, because as result of the temperature change the reaction rate will vary also.
Procedure
1. Be ready with your materials.
2. Put .1 mole of HCl in the beaker
3. Weight any that is less than 5g of Zinc; Keep it constant every trial.
4. Play the conductivity probe and drop the amount of Zinc that you measure at the
same time. The probe will play 180s.
5. Stir a little bit at the same speed for each trial.
6. After 180s pass, record the conductivity of Zinc at 30s, 60s, 90s, 120s, and 150s on
the data point table.
7. Repeat the step above but increase HCl by .3 moles.
The original goal is to investigate how the increasing ofconcentration of Hydrogen
chloride affects the conductivity when combine with constant Zinc mass.
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4. Graph of Reaction
The Conductivity at 4M of HCl
Experiment Zn (g) HCl Time(s) Conductivity(µS/cm)
Data point1 2 4M 30 29605
60 28931
90 28352
120 27632
150 27072
The Conductivity at 2 M of HCl
Experiment Zn (g) HCl Time(s) Conductivity (µS/cm)
Data point 2 2 2M 30 30771
60 30648
90 30629
120 30572
150 30524
The Conductivity at 1M of HCl
Experiment Zn (g) HCl Time(s) Conductivity(µS/cm)
Data point 3 2 1M 30 31094
60 31084
90 31046
120 30952
150 30942
The conductivity at .5M of HCl
Experiment Zn (g) HCl Time(s) Conductivity(µS/cm)
Data point 4 2 .5M 30 31198
60 31122
90 31110
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5. 120 31103
150 31008
The conductivity at .25M of HCl
Experiment Zn (g) HCl Time(s) Conductivity(µS/cm)
Data point 5 2 .25M 30 31008
60 30904
90 30771
120 30762
150 30696
Molar of HCl Conductivity rate(µS/cm.s)
4 2.532
2 3.425
1 3.447
.5 3.456
.25 3.425
Evaluating
To calculate conductivity rate, the five conductivities result must be add and divide
them each by 5. Now I get the average for each data point. What I want to get is that
by how much does the conductivity decrease per second for each data point.
4M of HCl
Sum = 113960/5 = 22792(Average)
Total time = 150 minute * 60 = 9000s
Conductivity rate = 2.532 µS/cm.s
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6. 2M HCl
Sum = 153144/5 = 30628.8(Average)
Conductivity rate = 30628.8/9000 = 3.403 µS/cm.s
1M HCl
Sum = 155118/5 = 31023.6(Average)
Conductivity rate = 31023.6/9000 = 3.447 µS/cm.s
.5M HCl
Sum= 155541/5 = 31108.2(Average)
Conductivity rate = 31108.2/9000 = 3.456 µS/cm.s
.25M of HCl
Sum = 154141/5 = 30828.2 (Average)
Total time = 150 minute * 60 second = 9000s
Conductivity rate = 30828.2/9000 = 3.425µS/cm.s
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7. Conductivity vs Time
30000
29500
29000
Conductivity
28500
28000
4 M HCl
27500 Conductivity(µS/cm)
27000
26500
0.0 50.0 100.0 150.0 200.0
Time
This graph is the result of the concentration of 4M of HCl reacting with 2 g of Zinc. Each
dot on the graph represents the conductivity after 30 second. In this reaction, the reaction
rate of the conductivity is 2.532µS/cm.s. The line is very straight compare others because
the reaction is very strong and fast.
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8. Conductivity(µS/cm) Vs Time
30800
30750
30700
Conductivity
30650
2MHCl Conductivity(µS/cm)
30600
30550
30500
0.0 50.0 100.0 150.0 200.0
Time
This graph represents the reaction of Zinc in 50 ml of 2M of HCl. There is a little curve in the
middle of the line. That’s because the reaction is much slower than the previous one. According
to the calculation, the conductivity rate is 3.403 µS/cm.s.
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9. Conductivity(µS/cm) vs TIme
31120
31100
31080
31060
31040
Conductivity
31020
31000 1 M HCl conductivity(µS/cm)
30980
30960
30940
30920
0.0 50.0 100.0 150.0 200.0
Time
The third graph show the conductivity over time when reacting 1M of HCl with Zinc.
Base on the graph, it shows that the reaction was very slow with round curve. From the
calculation, the rate at which the conductivity does down per second is 3.447 µS/cm.s
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10. Conductivity (µS/cm) vs Time
31250
31200
31150
Conductivity
31100
.5M HCl Conductivity (µS/cm)
31050
31000
30950
0.0 50.0 100.0 150.0 200.0
Time
This is the graph in which two gram of Zinc is reacted with .5M of HCl. The reaction of
Zinc in .5M of HCl is very weak that the reaction could hardly be seen in the middle of
the time or reaction. The conductivity rate in this reaction is 3.456 µS/cm.s.
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11. Conductivity(µS/cm) vs Time
31050
31000
30950
30900
Conductivity
30850
.25M HCl
Conductivity(µS/cm)
30800
30750
30700
30650
0.0 50.0 100.0 150.0 200.0
Time(s)
Unlike others graph, this graph look more like the first graph. The line it creates is very straight
line. We can see a little bit curve(stop) at around hundred second. In the reaction, it’s hard to if
the reaction whether the reaction occur because of too much H2O and too little HCl. Base on the
calculation, the conductivity rate for this reaction is 3.425µS/cm.s.
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12. Zinc(g) +/-.005 (Volume) +/- Uncertainty Uncertainty
.5 Zinc Volume
2 50 0.01 1
2 50 0.01 1
2 50 0.01 1
2 50 0.01 1
2 50 0.01 1
Conductivity rate
4
3.5
3
2.5
Conductivity rate
2
Conductivity rate
1.5
1
0.5
0
0 1 2 3 4 5
Molar of HCl
This graph represent the conductivity rate over the decreasing of the molar of HCl.
The conductivity rate decrease as the molar of HCl is increased.
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13. Conclusion
The goal of the experiment was to investigate how the change in the concentration of HCl affects
the electrical conductivity when the amount of Zinc is controlled. Base on the experiment, we
can acknowledge that when HCl and Zinc is reacted the conductivity decrease depend on how
much of each is used. The more HCl is used the less the conductivity, inversely is true. We also
know that H2O conduct more electric than HCl, which means the electrical current can flow
more rapidly through water although water is one of the substance or elements that conduct
electric. As the Molar of HCl is reduce therate of the conductivity seem to increase but the
reaction is fast when there is more HCl. The whole assumption is that difference of the rate of
the conductivity in which the molar of HCl is decreased in constant mass of Zinc is
.191µS/cm.s.
Improving the investigation
There are many factors that could be controlled better. Something that could be improve in this lab is that
the mass of Zinc, it mass be added the same amount as required in the lab. If some or even 1 mass is lost,
it could vary the data collecting. Even though exactly 50 ml is required, the exact millimeter might have
not been measure and that is one of the reason the data are not accurate. Actually this experiment should
be done by two people. Because someone must play the application for the conductivity while the other
drop Zinc, in that way the more accurate information could be recorded. The time is very important. It
need more time when HCl is decreasing, because the reaction will not start instantly if you have a few
molar of HCl. In that case, you need to wait for a long time to observe the reaction happen. Otherwise
your information is less accurate.
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