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Abstract:
Movie on 4-26-22 at 8.54 PM.movBackground:
Electrolytes were not covered during this year of Advanced Chemistry so far. Electrolytes grabbed me as a recognized chemistry topic that I didn’t have a great understanding of. I recognized similarities between the acid/base and electrolyte unit. Electrolytes are compounds that yield ions when dissolved in water, varying on strength based upon % dissociation. Acids are compounds that donate a proton while bases are compounds that accept a proton when dissolved in water. The basis for my experiment was that as a polar molecule, water is attracted to ions. When Phosphoric acid dissolves in water, hydrogen atoms will hydrate the phosphorus atoms, creating an electrical current within the solution. However, if a weak base was added simultaneously, the base’s hydroxyl group would attempt to receive the phosphorus ion and prevent conductivity. I conducted a competitive binding experiment where I kept the volume of distilled water and Phosphoric acid the same and added increasing levels of NaOH, a weak base, to prevent conductivity. Conductance measures the current passing through two electrodes one centimeter apart in a solution, and I used the Vernier Pro conductivity sensors to measure conductivity throughout the experiment. The unit for conductivity is (𝛍s/cm), or the microsimein, the reciprocal unit of resistance. In preliminary testing I examined the effect on conductivity that the addition of an electrolyte, and later a base, had on distilled water. Conductivity increased with the addition of Phosphoric acid and decreased with the addition of Sodium hydroxide, generating a signal for change in conductivity with electrolytes and weak bases.
Procedure:
Fig.2 (below right) Apparatus configuration for my experiment. Distilled water was used as the baseline substance for its lack of conductivity and polarization ability. Distilled water has a conductivity of 0.5-2 (𝛍s/cm). Distilled water that was recorded above the expected conductivity was calibrated for the experiment. 6 treatments with 5 trials each were run, with two negative control groups to examine the baseline conductivity of Phosphoric acid and Sodium hydroxide in distilled water. For each trial, distilled water was read for 20 seconds, then the Phosphoric acid and Sodium hydroxide were added simultaneously and stirred, conductivity was recorded after 40 seconds. Volumes for the base addition were determined in order to see the immediate, even parted, larger base volume, and baseline conductivities for the base and electrolyte. The sensor was wiped with a Kleenex between each trial to remove residue and limit uncertainty. The volumes of Distilled water and Phosphoric acid were determined because 30 mL of solution was needed to reach the probe’s internal sensor within its open slit. Fig.1 (top right) displays the probe’s sensor position. Multiple variables were controlled for the experiment. As temperature increases, conductivity increases, therefore room temperature was maintained. Concentration (M) of Sodium hydroxide and Phosphoric acid were controlled at 0.1 M for both solutions. Although conductivity plateaus after the solution was settled, conductivity was recorded at a constant time of 40 seconds after the addition of the electrolyte and base to keep a constant benchmark for recording.
(Fig. 1) Arrow points to internal probe sensor. 30 mL of solution was needed for the sensor to accurately record conductivity.
(Fig. 2) Apparatus set up for the base blocker experiment. Vernier Pro sensor connected to computer to read conductivity values throughout the addition of the electrolytes and base. Probe is held up on a stand and inserted into solution. At least 30 mL of the solution was recorded, with the volume determined by the required amount to reach the sensor inside the slit of the probes end.
Results:
(Fig. 3) Conductivity (𝛍s/cm) of H₃PO₄ and H₂O solutions with NaOH added. AAD plotted to display uncertainty in conductivity readings. As volume of NaOH(mL) increased, the conductivity(𝛍s/cm) of the solution decreased. H₃PO₄ control group measures conductivity of Phosphoric acid in distilled water. NaOH control group measures conductivity of Sodium hydroxide in water. 5 trials were run for each treatment, averages were calculated to represent values of each bar.
Results:
Figure 3 (above) displays that the base reduced the conductivity of the solution, but didn’t fully block conductivity. Conductivity decreased as NaOH volume increased, but conductivity remained high at the even volume treatment (average conductivity=2140.21 𝛍s/cm), displaying the electrolytes dominance compared to the base. The trial with comparatively more base reduced conductivity but could not fully block ion release in the water (average conductivity=323.40 𝛍s/cm). Therefore hydrated phosphorus ions charged the water, binding increasingly to hydroxyl groups as the base volume increased, but still creating a charge. The base was surprisingly also conductive (average conductivity 1002.42 𝛍s/cm) in the NaOH control group, likely due to the sodium ion available, a strong electrolyte. Unfortunately, sodium and phosphorus ions worked together to carry an electrical current. The uncertainty of the experiment was that the base contained Sodium ions that contributed to the conductivity of the solution positively. Further, to simultaneously add the two compounds of varying volume to the water added uncertainty, allowing the hydrogen ions to bind to the phosphorus ions earlier, giving a competitive advantage. If I did the experiment again I would choose a base that does not contain a strong electrolyte. This fix would truly examine if conductivity could be blocked without the blocker helping the electrical conductivity. Acidosis, a real world application of a ionic compound block attempt, is a common health problem that stems from a lack of base in the body. When our lungs and kidneys cannot maintain base levels, acidosis occurs. Doctors can predict acidosis by seeing the anion gap in a sample of electrolytes, and acidosis can be combated with Sodium bicarbonate, or baking soda injections, a common base.
Sources:
https://www.healthline.com/health/acidosis
https://www.healthline.com/health/alkalosis#prevention
https://www.britannica.com/science/conductivity
https://openstax.org/books/chemistry-2e/pages/11-2-electrolytes
https://openstax.org/books/chemistry-2e/pages/14-1-bronsted-lowry-acids-and-bases
https://ionode.com/en/theory/conductivity-theory
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