Electrical Conductivity And pH

Abstract

The aim of this experiment is to discover if there is any connection between ph and electrical conductivity. In order to achieve this, five solutions with varying ph levels were measured. With this, this experiment also shows the conductivity of baking soda, lemon juice, dishwashing detergent, milk and white vinegar.

From this experiment, the solutions from most acidic to least acidic were lemon juice, white vinegar, milk, baking soda and dishwashing detergent. This was the same order for the number volts conducted by each solution. From this we can see that as a solution becomes more acidic, its ability to conduct more electricity increases. In order to get a better understanding of the relationship between ph and electrical conductivity, more solutions with varying ph levels could have been used.

Aim

To investigate the relationship between ph and electrical conductivity within different household liquids.

Hypothesis

I believe that there is a relationship between ph and electrical conductivity. I think that as the solution becomes more acidic, the electrical conductivity. I trust that the lemon juice solution will conduct electricity the best. This will be measured through the volts measured by the multimeter. The order in which electrolytes I believe the most volts will be measured is lemon juice, baking soda, dishwashing detergent, milk and then vinegar. Vinegar is last because vinegar lacks free ions. Electrical conductivity is a result of free ions which can carry an electrical charge. Milk is second last because milk contains many ingredients. Milk is an emulsion or colloid of butterfat globules within a water-based fluid that contains dissolved carbohydrates and protein aggregates with minerals. (Anon., 2019). As it contains water it is second last on my list. Dishwashing detergent is next because I believe if detergent can conduct electricity, it will put people in danger when washing. Next, I think baking soda will be more conductive because when it dissolves in water, it is fully ionized and creates an ionic bond which allows it to carry charge from electrode to another. The best electrolyte I believe will be lemon juice as it contains citric acid which separates in water. This will allow the ions to flow through causing it to be able to conduct electricity well.

Research

When an electrical current pass through a wire, what actually moves and carries the current is electrons. But in solutions, the current is carried by ions: positively charged cations and negatively charged anions. The conductivity of a solution depends on the concentration of all the ions present; the greater their concentrations, the greater the conductivity. These ions all have the electrical unit charges shown by their symbols, but they move at different velocities through the solution, so they contribute differently to the conductivity. Of the common ions, the most mobile cation is the Hydrogen ion and the most mobile anion is the Hydroxyl ion. So, you see that strongly acidic solution will have high conductivity since the pH is a measure of the concentration of the Hydrogen [and the Hydroxyl] ions, for an acidic solution, the lower the pH the greater the conductivity will be.

Lemon Juice-Lemon mainly consists of citric acid which means that it is an acidic substance. One of the main qualities of being an acidic substance is that acids easily break up when it dissolves in water into charged anions and cations. These charged particles allow for lemon juice to be able to become a good choice for an electrolyte. Lemon juice also reacts well with metals being able to chemically bond with them and uses the redox reaction.

Baking soda - Baking soda is an excellent electrolyte for this experiment as because when it dissolves in water, it is fully ionized and creates an ionic bond which allows it to carry charge from electrode to another. It has the chemical composition NaHC03 and can split into sodium and bicarbonate ions which allow it conduct electricity well.

Dishwashing detergent-Dishwashing detergents contain many different materials though the main is water itself although it contains many different types of salts which make it able to conduct electricity. Like mentioned above, salt can form ions which allow it to conduct electricity which also applies for dishwashing detergent.

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• Milk - Electrical conductivity of milk is mainly due to its soluble salt fraction. Even though lactose does not conduct electricity and fat decreases conductivity, proteins and peptides have somewhat of an importance for milk to be conductive. However, fermentation of lactose to lactic acid sharply increases conductivity.
• Vinegar - Vinegar, which is an acid, produces free ions in solution. These ions carry charges from one place to another, which is how current is carried. Vinegar is mostly water with a small amount of acetic acid in it. The acetic acid separates into ions so that the solution conducts electricity.

Discussion

This experiment tested the relationship between ph and the electrical conductivity between household liquids. There is no clear answer to this relationship as some think that they do have a connection, and some think they don’t. Even though there were a few flaws in the experiment, we are able to learn more about the relationship between ph and electrical conductivity.

In my experiment, both baking soda and the dishwashing detergent had the same ph levels, but the number of volts passed through the baking soda was 0.02 volts more than the dishwashing detergent. I believe multiple factors caused this, one of which was due to the various chemicals present in dishwashing detergent. Baking soda is a compound because it is composed of molecules that are all identical. On the other hand, dishwashing detergent is made from several things such as a viscosity regulator, ph regulator, preservatives, fragrances, dyes, additives and many other chemicals.

Another confounding factor is that the ions present in dishwashing detergents. ph is a measurement of the hydrogen ions present in a liquid. It is possible that due to the various chemicals in the dishwashing detergent, there may be different ions which are changing the ph of the dishwashing detergent. Moreover, the volts conducted by the baking soda is more because of the number of free ions present in baking soda is more compared to the dishwashing detergent. This is because the different mixtures may have balanced the free ions in the dishwashing detergent. This problem could be fixed in later experiments by making the household liquids by hand. By making it yourself, we are able to control what goes into the solution and if any impurities are in the solution. Also, there would be no added chemicals in the solution which limits the amount of free ions present.

Another problem was that there wasn’t enough data. If there was a solution for every ph, we would be able to see the full relationship between ph and electrical conductivity. From the results tabulated above, we are able to see that as the solution becomes more acidic, the electrical conductivity increases. This problem can be solved in future experiments by having more solutions to test to see the full relationship between ph and electrical conductivity.

A solvable problem was putting the nails in the container. The original plan was to poke the nails through the plastic container. This resulted in big cracks on the side of the plastic container. It was evident that if any liquid were to be poured into the container there would be a big leak. This was solved by adding sticky tape to the materials. The sticky tape made the nails stick to the inside of the container so that there were no cracks.

Overall the experiment was accurate, reliable and valid. Due to many trials of the electrical conductivity, this experiment is deemed reliable as the average is accurate. The experiment was valid because there were many controlled variables than the uncontrolled and the measuring equipment was accurate. This experiment could be used for scientists to see if there is a relationship between ph and electrical conductivity. (Brunker, n.d.)

For future experiments, there should be more solutions, the solutions should be made by hand so that no impurities and other chemicals are added, and a sturdier container could be used.

Conclusion

In conclusion, the relationship between ph and electrical conductivity was achieved. My hypothesis stated that as the solution became more acidic, the conductivity of that solution also increased. This was proven due to the results collected from this experiment. I also stated that lemon juice will conduct the most electricity. This was also demonstrated as lemon juice had the highest conductivity with 0.19 volts. Future studies could be conducted to aid in characterising the environment.

References

1. (Sahoo, 2014) Adam, H. a., 1995. Cellmax. [Online] Available at: https://www.cellmax.eu/ph-and-electric-conductivity/
2. Bruckner, M. Z., n.d. Water and Soil Characterization - pH and Electrical Conductivity. [Online] Available at: Microbial life
3. Sahoo, P., 2014. Research Gate. [Online] Available at: https://www.researchgate.net/post/Is_there_any_relationship_between_pH_and_conductivity_of_a_solution
4. SJ, W., 1996. Determination of the relationship between the pH and conductivity of gastric juice.. [Online] Available at: https://www.ncbi.nlm.nih.gov/pubmed/8746373
5. Smallwood, R., n.d. IOP Science. [Online] Available at: https://iopscience.iop.org/article/10.1088/0967-3334/17/1/002/pdf