In this assignment we will be focusing on one property, which influences the electrical conductance of an ionic solution. Compounds can be held by a covalent or ionic bond, which depends on the nature of the bonds. In case of ionic compounds (we also call them electrolytes), the force of attraction is present between the ions, which have opposite charge. One of the ions has a positive charge, which is called a cation, and the other has a negative charge, which is called an anion. This attraction is called an ionic bond. Ionic compounds1 form crystals in which anions and cations are held together with force of attraction. Ionic compounds are also known as salts mostly. They are usually hard and brittle. They are solid at room temperature and they have high melting and boiling points. They conduct electricity in solution because they dissociate into ions when dissolved in water, which are free to move. These ions carry the electrical charge from the anode to the cathode.
Properties of salt solutions, which influence their electric conductance:2
The temperature of the solution.
The magnitude of the charge on the ions.
The concentration of the ions in the solution.
The liquid used to dissolve the ionic substances in.
The size of the ions.
I would like to investigate that how the concentration of the ions in the solution affects the electric conductance of the solution.
Aim Our aim is to figure out the answer of the research question through this experiment
Research question What is the relationship between the conductivity of the ionic solution and concentration of the ionic compound (electrolyte)?
When an ionic compound dissolves in water, the ions usually break apart and diffuse throughout the whole solution. Ions conduct electricity because they are mobile and carry charge with them. In this case, the ionic compound (NaCl) will be dissolved in water, this causes the ions (Na+ and Cl-) to diffuse in the solution and resulting in them conducting electricity. It happens because the sodium holds one excess electron and Chlorine is in need of one electron, resulting in sodium giving one electron to Chlorine when they get separated. As a result of this, the Chlorine becomes electrically negative and the Sodium becomes positive. This is the chemical reaction which occurs-
NaCl(s) ? ï¿½ ? Na+(aq) + Cl-(aq)
When we put electrodes in the solution, the positive ions (Na) will migrate to negative electrode and negative ions (Cl) towards the positive electrode that’s how electric current will flow.
The conductivity of a solution depends on the concentration of the solution. In water, it is the ions that pass electricity from one to the next. This means that the more Na+ and Cl- contained in water the more electricity is carried, and the higher the conductivity. If the solution of water and NaCl is more concentrated (NaCl in large amount), its electric conductance will be more than if the solution is less concentrated (NaCl in a smaller amount). Therefore in my opinion, the greater the concentration of the ions, the more the conductivity of the solution will be.
Controlled variables: temperature, voltage applied (in this case 10 volts), the electrolyte (Nacl) used with water to make a solution.
Independent variables: The concentration of NaCl solution and volume of water.
Dependant variables: Electric conductance measured by an ammeter.
Plan for experiment
In this experiment we will be using NaCl solution as the ionic compound (electrolyte). We will be placing the electrolyte in water as to create a concentrated solution. Different amounts of NaCl and water shall be mixed to prepare the solutions, which have different concentrations so we can compare the electric conductance in different cases. This giving us an idea of how the electric conductance of the solution would change when the concentration of the solution is increased or decreased. So then from the experiment we can draw a conclusion on how the concentration of a solution affects the conductivity of an ionic solution.
Two electrodes are placed and a potential is applied across the electrodes. Then electric current is measured, which passes through the solution. The electric conductance facilitates by the charge on ions. So we can say that the conductivity of the solution is directly proportional to the concentration of its ions.
Electrodes made of copper
Lab coat ( 2 sizes available small and large)
Demineralized water – 425 ml in a washbottle as to make it easier to be more accurate while pouring water in the beakers
NaCl – 75 ml
Voltage Power supply
Experimental set-up Diagram
Steps of the experiment:
1. Wear lab coat to prevent clothes from any damage, which can be caused.
2. Wear goggles for safety measures.
1. Make sure all the materials are present.
2. Take out 4 glass beakers and set them out on the table.
The solution chosen is NaCl. In the five different beakers, there will be different amounts of water and different amount of concentrations of NaCl will be added. The amount of water will decrease with the increase of concentration as to keep the same volume of the solution, which is 100 ml in total for all 5 cases.
These 5 solutions are prepared in 5 different beakers. We use a measuring cylinder to measure the amount of water and measuring beaker for NaCl solution.
1. 1st solution -Take 95ml water in a beaker and then add 5ml of NaCl solution.
2. 2nd solution – Take 90 ml water and then add 10ml of NaCl Solution.
3. 3rd solution – Take 85 ml of water and then add 15 ml of NaCl Solution.
4. 4th solution – Take 80ml water and then add 20 ml of NaCl solution.
5. 5th solution – Take 75 ml of water and then add 25 ml of NaCl solution.
Measuring the conductivity / amount of electricity created
1.To measure the electric conductance, we need to first create a circuit by using a pair of copper electrodes. The electrodes are supposed to be placed on an electrode holder, and tightened with clamps.
2. Connect the electrodes with a wire to the ammeter and also with the power supply.
3. Immerse the electrodes in the beaker.
Note: Keep the electrodes as far apart as possible (2 – 3 inches), don’t let them touch or the power module will be damaged.3
4. Now turn on the voltage power supply and make sure to put the current limitation to maximum so that there is no interference at all with the result.
Note: Do not touch the electrodes after the power supply is turned on.
5. To control the amount of voltage turn the button to 10 volts, it doesn’t matter how many volts are applied as long as the value is kept the consistent throughout the whole experiment.
6. Monitor the conductivity of the solution for 4-5 seconds on the ammeter until it become stable.
1. Record the conductivity value in your data table.
2.Make sure to clean the electrodes after taking measurement.
3. Then place the electrodes into 2nd, 3rd and 4th and 5th solutions respectively and record the conductivity in the table for each case.
1. Empty all the beakers in the sink then wash and dry them.
2.Remove ammeter from the electrodes.
3.Dry up the electrodes with tissue.
4.Place all materials back into the cupboards.
Data and Observations
Amount of NaCl (in ml)
Conductance (in amperes)
Amount of water (in ml)
The graph shows the relationship between the amount of Nacl and the conductance.
The line represents the conductance.
Results: I’ve presented all my data in form of a graph, it will show the co-relation between the conductivity4 and concentration 5of salt solution. On the horizontal axis I have placed the Nacl concentration and on the vertical axis the conductivity of the solution. We can then draw a conclusion after looking at it.
After doing the experiment, I can conclude that if an electrolyte is dissolved in water, it completely dissociates into ions and the electrolyte would contribute to conduction of electricity to the solution. In this experiment, NaCl dissociates into Na+ and Cl- ions, which made it possible for water to conduct electricity. The conductivity of the solution depends on the concentration of the electrolyte and behaves differently for different concentration of the electrolyte. As we can see by the graph, if we start increasing the concentration of the electrolyte (NaCl), the electric conduction will be increasing accordingly. So we can get to the conclusion that the conductivity of the solution is directly proportional to the concentration of the electrolyte solution.
In overall I find that this experiment went very well. My hypothesis turned out to be as I had assumed it would, as the conductance did increase with the increase of concentration. Although there was mistake we did at first, which was creating the wrong circuit by connection the wrong wires which caused the conductance on the ammeter to be show in negative. However we soon figured out our mistake and then re did the circuit after which we got successful results.
My results are reliable up to an extent as we tried to make our experiment as accurate as possible. We made sure that no extra solution was left on the electrode holder whiles taking measurements by cleaning them so that the conductance wouldn’t be affected. Also we applied the same amount of energy to each solution so that it wouldn’t contribute to the conductance. During measuring the amount of water we took a considerably accurate account and tried to make sure that there wasn’t a big difference.
However there were a few things we could have done better to get even more reliable results. We could have taken an average of the readings of the solutions whose conductance kept changing and wouldn’t become stable. Also a larger gap could have been taken between the amount of concentrations such that to assist in making conclusions in a much easier way.
We tried to consume as less time as possible and were able to finish our experiment in sufficient time. In my view we were also extremely organized in the experiment as we knew exactly what we had to do , and any small mistakes which we made we were able to solve them.
There should be reasonable difference in the concentrations of the NaCl solutions used for the experiment to get more reliable result.
Keep electrodes for sometime in each solution, and as soon as the reading is stable, note it down on your table.
Stir the solutions properly before putting electrodes into it to make sure that NaCl has mixed properly with water in each case.
Clean and dry electrodes before putting them into different solutions.
The amount of the voltage applied should be the same in each case.
Follow up Experiment:
We are investigating on the various factors that influence the conductance of an ionic solution. In this experiment we concentrated on how the concentration of a solution affected the conductance. So the follow up experiment should be focusing on another influential factor, which in my view should be how temperature influences the conduction of an ionic solution. I also find this a really interesting topic to continue investigation on. This experiment will give us an even better understanding of conductance and electrolytes.
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4 “Conductivity of Electrolytic Solutions.” UCS Home. Web. 13 Dec. 2009. <http://www-ec.njit.edu/~grow/conductivity.htm>.
5 “Concentration -.” Wikipedia, the free encyclopedia. Web. 13 Dec. 2009. <http://en.wikipedia.org/wiki/Concentration>.