Kno3 Solubility Lab
The investigation was designed to determine the effect of the addition of increasing concentrations of a miscible liquid (ethanol) on the solubility of KNO3 in water. The results of the investigation support the hypothesis that water, which exhibits greater polarity, is able to dissolve a greater mass of KNO3 at lower temperatures compared to tested concentrations of Ethanol ranging from 12.5% to 30%. Furthermore, the results of the graph 1 show correspondence to the dielectric constant of each solvent as both the starting solubility of the solubility curves and the dielectric constant of the solvent decreases from trendline 1 (0% Ethanol) to trendline 4 (30% Ethanol).
According to Graph 1, an inversely proportional relationship is clearly demonstrated between the concentration of ethanol and the solubility of KNO3 …show more content…
as when the concentration of ethanol increased, the solubility of Potassium Nitrate had consequently decreased.
It was noted that each trendline of graph 1 displays a clear exponential relationship indicated by strong R^2 values, between 0.974 and 0.995. This exponential trend demonstrates the proportional relationship between the two variables of temperature and solubility, simply stating that the solubility of KNO3 increases exponentially with temperature. For instance, in trendline 1 (0% Ethanol), the first data point at 0 degrees has a solubility of 19.75 grams/100grams of H20 compared to the data point at 60 degrees with a solubility of 120 grams/100 grams of H20. This comparison itself shows the effect of temperature on the solubility of KNO3, demonstrating how rapidly solubility increases with temperature. While all trendlines display this same relationship, they all have different y-intercepts (or known as the starting solubilities). Trendline 1 illustrating the solvent with 0% Ethanol (100% water) is situated at the top of
the graph with the highest y-intercept of 19.747. Conversely, the solution with the greatest ethanol concentration of 30% is saturated at 6.4105 grams of KNO3 at 0 degrees per 100 grams of solution. The percentage difference between these values from the lowest concentration to the highest concentration of ethanol is -101.97%. Thus, trendline 4 (30% Ethanol) requires 60 degrees Celsius to dissolve 19.747 grams of KNO3 compared to only needing 0 degrees for trendline 1 (0% Ethanol). Additionally, it can be established that the slope of each trendline is kept consistent through the results at 0.03 possibly suggesting how sensitive the solubility change is towards temperature.
In this investigation, there were systematic errors present that may have affected the accuracy and validity of the results. One data point that could be considered an outlier from graph 1 is the last data point on trendline 1 (68.9 degrees with a solubility of 128.89) as it was observed to deviate significantly from the exponential trend line. More specifically, if this data point had followed the trend, at 68.9 degrees the solubility would be 156 having a percentage difference of 19.03% with the experimentally derived value. This is a significant outlier as the percentage differences for the other values between the values from the experiment and the values from the calculated regression line is about 3-4%. This outlier is the reason for the R^2 value of trendline 1 to be lower than the other trendlines. This may have been a result of only one trial conducted for this set limiting the reliability of data, so executing three trials would minimise the effect of confounding variables and thus, improve the validity of the results.
During this experimental investigation, the primary source of error that frequently occurred was determining the time at when KNO3 recrystallized, primarily depending on an individual’s reaction time. This could be refined in future experiments by utilising electronic data logging technology to monitor concentration in situ or by having more observers monitor the KNO3.
Furthermore, the positioning of the thermometer in the test tube may have been a source of error. As a result of the thermometer used as a stirring rod, it often had touched the glass test tube where the temperature measured would have been much higher. This is due to the test tube being moderately hotter as it was submerged in boiling water. An improvement to this would be using a stirring rod instead of a thermometer in an attempt to eliminate any disruptions to the actual temperature measurement. Moreover, the temperature at the bottom where the crystals are forming may not necessarily be the temperature of the solution where the end of the thermometer is. The thermometer itself may also be slightly inaccurate due to a limitation of having ± 0.5 degrees of uncertainty, which this uncertainty would increase as the experiment progressed and when calculating averages. Another factor would be the‘lag time,’ as this would give a false recording of temperature that is higher, resulting in a saturation temperature that is too high for a lower level of solubility.
Additionally, when the solution was heated to dissolve the KNO3 crystals, some might not have been entirely dissolved before the solution was taken out of the hot water bath. Hence, some of these existing, undissolved crystals still present in the test tube may have prematurely encouraged the formation of crystals before the solution reached the temperature at which it was saturated. This could have been stringently prevented in future experiments by mortaring the salt to increase the surface area for the heat to dissolve all the KNO3 present in the test tube.
Before the saturation temperatures were measured, some water may have evaporated from the test tubes. Evaporation usually increases the solution concentration causing a decrease in the observed solubility of the sugar. Consequently, this corresponding saturation temperature will be too high because the increased level will cause the solute to fall out of solution sooner than expected moving the graph up. Thus, in future experiments, evaporation could be prevented by attaching a lid or a cover to the test tube.
Understanding the properties of the solubility of a salt (KNO3) in a water-ethanol solution acts as a basis for real-world applications as many more alcohols and concentrations are used with different solutes. Hence, this experiment had only dealt with a narrow subset of possibilities compared to what occurs in the scientific reality. Thus, follow-on investigations such as experimenting with different alcohol-water solvent mixtures would help individuals to understand the significance of this frequently used solvent in the medical and cosmetic field. For instance, solvents used for many dosage forms in pharmacology are alcohol-based where understanding the solute-solute, solvent-solvent and solvent-solute interactions is vitally important to prevent life-threatening drug precipitation or incorrect dosage administration. So experimenting with KNO3 and the miscible solvent solution of water-methanol with the same proportions could be a future investigation to determine the effect of a different alcohol on the solubility of KNO3.
Conclusion
Thus, the aim to study the effect of a miscible liquid (a water-ethanol solution) on the solubility of Potassium Nitrate (KNO3) has been achieved through this investigation. Additionally, the expected hypothesis has been supported as it had been found that the solubility of Potassium Nitrate in the miscible solution of water+ethanol at a constant temperature decreases with increasing the mass percent of Ethanol. The trend is also along with the decreasing of the dielectric constant of the mixed solvent.
According to Graph 1, an inversely proportional relationship is clearly demonstrated between the concentration of ethanol and the solubility of KNO3 …show more content…
as when the concentration of ethanol increased, the solubility of Potassium Nitrate had consequently decreased.
It was noted that each trendline of graph 1 displays a clear exponential relationship indicated by strong R^2 values, between 0.974 and 0.995. This exponential trend demonstrates the proportional relationship between the two variables of temperature and solubility, simply stating that the solubility of KNO3 increases exponentially with temperature. For instance, in trendline 1 (0% Ethanol), the first data point at 0 degrees has a solubility of 19.75 grams/100grams of H20 compared to the data point at 60 degrees with a solubility of 120 grams/100 grams of H20. This comparison itself shows the effect of temperature on the solubility of KNO3, demonstrating how rapidly solubility increases with temperature. While all trendlines display this same relationship, they all have different y-intercepts (or known as the starting solubilities). Trendline 1 illustrating the solvent with 0% Ethanol (100% water) is situated at the top of
the graph with the highest y-intercept of 19.747. Conversely, the solution with the greatest ethanol concentration of 30% is saturated at 6.4105 grams of KNO3 at 0 degrees per 100 grams of solution. The percentage difference between these values from the lowest concentration to the highest concentration of ethanol is -101.97%. Thus, trendline 4 (30% Ethanol) requires 60 degrees Celsius to dissolve 19.747 grams of KNO3 compared to only needing 0 degrees for trendline 1 (0% Ethanol). Additionally, it can be established that the slope of each trendline is kept consistent through the results at 0.03 possibly suggesting how sensitive the solubility change is towards temperature.
In this investigation, there were systematic errors present that may have affected the accuracy and validity of the results. One data point that could be considered an outlier from graph 1 is the last data point on trendline 1 (68.9 degrees with a solubility of 128.89) as it was observed to deviate significantly from the exponential trend line. More specifically, if this data point had followed the trend, at 68.9 degrees the solubility would be 156 having a percentage difference of 19.03% with the experimentally derived value. This is a significant outlier as the percentage differences for the other values between the values from the experiment and the values from the calculated regression line is about 3-4%. This outlier is the reason for the R^2 value of trendline 1 to be lower than the other trendlines. This may have been a result of only one trial conducted for this set limiting the reliability of data, so executing three trials would minimise the effect of confounding variables and thus, improve the validity of the results.
During this experimental investigation, the primary source of error that frequently occurred was determining the time at when KNO3 recrystallized, primarily depending on an individual’s reaction time. This could be refined in future experiments by utilising electronic data logging technology to monitor concentration in situ or by having more observers monitor the KNO3.
Furthermore, the positioning of the thermometer in the test tube may have been a source of error. As a result of the thermometer used as a stirring rod, it often had touched the glass test tube where the temperature measured would have been much higher. This is due to the test tube being moderately hotter as it was submerged in boiling water. An improvement to this would be using a stirring rod instead of a thermometer in an attempt to eliminate any disruptions to the actual temperature measurement. Moreover, the temperature at the bottom where the crystals are forming may not necessarily be the temperature of the solution where the end of the thermometer is. The thermometer itself may also be slightly inaccurate due to a limitation of having ± 0.5 degrees of uncertainty, which this uncertainty would increase as the experiment progressed and when calculating averages. Another factor would be the‘lag time,’ as this would give a false recording of temperature that is higher, resulting in a saturation temperature that is too high for a lower level of solubility.
Additionally, when the solution was heated to dissolve the KNO3 crystals, some might not have been entirely dissolved before the solution was taken out of the hot water bath. Hence, some of these existing, undissolved crystals still present in the test tube may have prematurely encouraged the formation of crystals before the solution reached the temperature at which it was saturated. This could have been stringently prevented in future experiments by mortaring the salt to increase the surface area for the heat to dissolve all the KNO3 present in the test tube.
Before the saturation temperatures were measured, some water may have evaporated from the test tubes. Evaporation usually increases the solution concentration causing a decrease in the observed solubility of the sugar. Consequently, this corresponding saturation temperature will be too high because the increased level will cause the solute to fall out of solution sooner than expected moving the graph up. Thus, in future experiments, evaporation could be prevented by attaching a lid or a cover to the test tube.
Understanding the properties of the solubility of a salt (KNO3) in a water-ethanol solution acts as a basis for real-world applications as many more alcohols and concentrations are used with different solutes. Hence, this experiment had only dealt with a narrow subset of possibilities compared to what occurs in the scientific reality. Thus, follow-on investigations such as experimenting with different alcohol-water solvent mixtures would help individuals to understand the significance of this frequently used solvent in the medical and cosmetic field. For instance, solvents used for many dosage forms in pharmacology are alcohol-based where understanding the solute-solute, solvent-solvent and solvent-solute interactions is vitally important to prevent life-threatening drug precipitation or incorrect dosage administration. So experimenting with KNO3 and the miscible solvent solution of water-methanol with the same proportions could be a future investigation to determine the effect of a different alcohol on the solubility of KNO3.
Conclusion
Thus, the aim to study the effect of a miscible liquid (a water-ethanol solution) on the solubility of Potassium Nitrate (KNO3) has been achieved through this investigation. Additionally, the expected hypothesis has been supported as it had been found that the solubility of Potassium Nitrate in the miscible solution of water+ethanol at a constant temperature decreases with increasing the mass percent of Ethanol. The trend is also along with the decreasing of the dielectric constant of the mixed solvent.