The Effect of Temperature Change During the Dilution of a Strong Acid
Introduction
According to the Brønsted-Lowry acid-base theory, an acid is a reactant that loses a hydrogen ion to another reactant. A strong acid is when virtually all the molecules of the acid ionises in water. In this experiment, the strong acid used was hydrochloric acid. This acid is formed when gaseous hydrogen chloride reacts with water according to the equation:
When in solution, the hydronium and chloride ions formed will be partially surrounded by water molecules via ion-dipole bonds, an electrostatic force of attraction that exists between charges in the ions and the partial charges in the water molecules. Water molecules surrounding ions is called hydration.
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The process of solvation involves the breaking of bonds between solute molecules, the breaking of intermolecular attractions between solvent molecules, and the formation of new solute-solvent attractive bonds. Energy is needed to break bonds and energy is released in the formation of bonds. It is known that when diluting a strong acid into water, an increase in temperature is observed. As there products are not formed, the change in temperature must come from the further formation of ion-dipole bonds between partially hydrated ions in the acid solution and the water molecules in the water. Concentration refers to the amount of solute dissolved in a given amount of solution or solvent. A high concentration of acid corresponds with more hydronium and chloride ions in solution. However, this also means that fewer water molecules are available to surround each ion. It follows that the less concentrated the solution of acid, the more water molecules surrounding these ions. That is, the more hydrated an ion, the fewer water molecules that will further hydrate the ion, resulting in the formation of fewer ion-dipole bonds that will form. When bonds form, the potential energy of the products decreases. The difference between the potential energy of the products and reactants is released primarily as heat energy into the surroundings, in this case, it is the surrounding particles. This transfer of energy increases the kinetic energy of these particles, increasing the average kinetic energy of the particles, thus increasing the temperature of the surroundings. This evidence of an exothermic reaction. Hypothesis If the concentration of acid increases, then there will be a greater, positive change in the temperature of the solution. Variables Independent Variable The independent variable was the concentration of the acid used. This was changed by using the same sample of acid and then diluting the acid to lower concentrations when needed. Dependent Variable The dependent variable was the change in temperature experienced by the solution. This was measured by using a thermometer. Controlled Variables A variable that was controlled in the experiment was the type of acid used.
The strong acid used in the experiment was hydrochloric acid. Using different types of acid would mean different ions present in solution. This means that there will be different sized ions, meaning that there will be space for different numbers of water molecule. Only using the hydrochloric acid would allow for consistent hydration, as all the ions would be the same size and would provide the same number of molecules to hydrate them. Another controlled variable was the volume of water used. This allows the same number of water molecules available to hydrate the ions in the acid solution. It also means that there will be the same mass of water available to conduct the heat energy released from …show more content…
hydration. Method Cotton balls were put into a large copper container and a small copper container was placed into the larger container until there was enough cotton to surround the small container. A hole was made in the middle of the polystyrene lid so the thermometer would fit in. 40 mL of deionised water was measured in a measuring cylinder and poured into the small copper container. 40 mL of 10 mol/L hydrochloric acid was measured in a separate measuring cylinder and poured into the container. The polystyrene lid was immediately placed over and covered the large copper container and the thermometer was used to stir the solution. The greatest, registered temperature was recorded and the solution was discarded. This was repeated two more times and the results were averaged. Once all three trials were completed for the 10.0 mol/L concentration of acid, 8.00 mol/L acid was made and experimented under the same conditions as the 10.0 mol/L acid. 6.00, 4.00, 2.00, and 0.00 mol/L acids were also made and used in the experiment. Analysis of Results The experimental results show a positive, linear trend between the concentration of acid and the change in temperature in the resulting solution. The highest concentration of acid, 10 mol/L, produced the greatest average change in temperature of 9.17 °C. This trend was consistent and followed through down to the lowest concentration, 2.00 mol/L, which produced the lowest average change in temperature of 2.37 °C. The concentration 0.00 mol/L, was water and served as a control in the experiment as a way to test if it was the acid alone producing the change in temperature. Even though this concentration resulted in the lowest average change in temperature, the thermometer should not have registered any change in temperature at all. This may have been a result of the friction between water molecules when more water was being added. The fact that this produced a low change in temperature suggests that the temperature change from the act of pouring a solution into a liquid is negligible compared to the hydration of ions experienced by the other concentrations of acid. Evaluation Sources of Error The measuring cylinder used had an uncertainty of ± 1°C at 25°C (displayed on the cylinder). While the results obtained were somewhat consistent, using a more accurate measuring device with a lower uncertainty would provide more reliable and possibly more precise results. A volumetric pipette would be a suitable replacement. During the dilution of 10 mol/L acid to lower concentrations, a change in temperature was observed.
However, the increased temperature of the new acid solution was at a greater temperature than the ambient temperature and the temperature of the water. This suggests that some of the results obtained were partially due to the fact that some of the heat energy of the acid was transferred to the water, as well as the hydration of ions present in solution. An improvement would be to create the solutions of desired concentration and allow them to reach thermal equilibrium with the surroundings. This would allow more accurate results and the allow for the assumption that the temperature change observed during the experiment would only be due to hydration of
ions. A copper container was used as the reaction container in the calorimeter. Copper is an inert metal and an excellent thermal conductor, meaning that some of the heat generated from the dilution was conducted by the copper. This would mean that the temperature measured is less than the real temperature. Polystyrene is an inert solid and is also a poor conductor, meaning it would be a more suitable substitute to copper. As such, it will reduce the exchange of energy from the contents in the container and surroundings. If there is a temperature change in the contents, the polystyrene will minimise the loss or gain of heat energy from the cup. Validity and Reliability of Data All the results obtained from the experiment closely follows the line of best fit and an absence of outliers suggests that any flaws in the experiment impacted insignificantly and that errors were consistent throughout. Using the ideas from solvation, the ions present in the acid solution are partially hydrated by the available water molecules. When more water molecules are available, the partially hydrated ions will be further hydrated. This suggests that the more concentrated the acid solution, the more ion-dipole bonds formed and the more heat generated, thus a greater change in temperature when diluting in water. The lower the concentration of acid, the more hydrated the ions present in the solution, therefore fewer ion-dipole bonds will form and more heat will be generated, thus less change in temperature will be observed during dilution. The positive, linear relationship between acid concentration and the change in temperature of the water found in the experiment, where increasing the concentration would increase the change in temperature of the diluted acid, supports the theoretical trend. Improvements In addition to resolving the errors present in the experiment, ways to obtain more accurate and conclusive data would be to increase the sample size by testing more concentrations of hydrochloric acid. Experimenting with other strong acids, such as sulfuric and nitric acid, would also increase the sample size and will allow for more results, potentially support the question proposed. Repeating the experiment would decrease random results from occurring, further reducing potential outliers and making the measured results more precise. Conclusion The purpose of the experiment was to investigate the effects of concentration of a strong acid and the temperature change during dilution. The experiment showed that increasing the concentration of a strong acid results in a greater change in temperature in water, where the greatest concentration of acid, 10.0 mol/L, produced the greatest average temperature change, 9.17 °C, and the lowest concentration of acid, 2.00 mol/L, produced the lowest average temperature change, 2.37 °C. The hypothesis that increasing the concentration of acid would increase the change in temperature in the water is supported by the data obtained from the experiment. Looking at the results obtained from the experiment, the consistency and limited deviation from the line of best fit suggests that the experimental results are close to the real results.
Two equations were used in this experiment to determine the initial temperature of the hot water. The first equation
Paragraph 2: It is believed that as the temperature of the water increases the time it will take for the tablet to dissolve will decrease. This is believed since the temperature there will be more energy allowing the particles to get together and form a reaction allowing the ta...
Input variables In this experiment there are two main factors that can affect the rate of the reaction. These key factors can change the rate of the reaction by either increasing it or decreasing it. These were considered and controlled so that they did not disrupt the success of the experiment. Temperature-
First, a calorimeter was constructed with three standard styrofoam cups. One cup was stacked within the second for insulation, while the third cup was cut in half to be used as a lid. The lid was made to increase accuracy when recording the temperature. The temperature probe hooked up to Logger Pro software poked a hole in the top of the calorimeter by applied force with the end of the probe through the Styrofoam. Meanwhile, 40mL of deionized water were measured out in two clean 50 mL graduated cylinders, and poured into 100 mL beakers. The beakers and graduated cylinders were cleaned with deionized water to avoid contamination that may cause error. One of the beakers was placed onto a hot plate, which was used to heat the water in the beaker. The other beaker rested at room temperature. Once heated and at room temperature, the initial temperature was measured with the probe. Next, the two 40 mL of deionized water were poured into the calorimeter, quickly sealed with the lid, and the temperature probe emerged through the top of the calorimeter into the water to measure the temperature so the calorimeter constant would be determined. The equations used to determine the calorimeter constant were Δq = mCΔT and Δq =
In the pH homeostasis lab, 6 experiments were conducted. The hypotheses were: If base is added to water then the pH will increase; If acid is added to water then the pH will decrease; If base is added to homogenate, then the pH will increase; If acid is added to homogenate, then the pH will decrease; If acid or base is added to buffer, then the pH will remain the same. After the experiments were conducted, the graphs were somewhat similar to the hypotheses.
The purpose of the lab is to understand how to calculate the calorimeter constant by using a calorimeter. This allows us to analyze the heat reaction of different substances. Calorimetry is a word that comes from both Latin and Greek. The prefix “Calor” in Latin signifies heat and the suffix “metry” in Greek means measuring. Therefore the word itself translates to measuring heat. Joseph Black, was the first scientist to recognize the difference between heat and temperature. Energy is always present in chemical and physical changes. The change of energy that occurs when there is a chemical change at constant pressure is called enthalpy. Enthalpy changes , as well as physical and chemical changes, can be measured by a calorimeter. The energy that is released or absorbed by the reaction can be either absorbed or released by the insulating walls of the instrument.
The sought to determine the effects of mixing various levels of acids and bases to see which combination would have the most explosive reaction, and measure the resulting pH levels. I did this by testing an assortment of different pH levels of acids and bases, mixing them together and measuring the results. Most of the experiments resulted in a pH neutral solution, except for the Sulfuric Acid and the Sodium Hydroxide. By far, the Sulfuric Acid was the most explosive, followed by the Citric and Acetic acid.
Introduction: A phase change is a result from the kinetic energy (heat) either decreasing or increasing to change the state of matter (i.e. water, liquid, or gas.) Thus saying, freezing is the phase change from a liquid to a solid which results from less kinetic energy/heat. Also, melting is the phase change from a solid to a liquid which results from adding kinetic energy/heat. So, the freezing and melting point of something is the temperature at which these phase changes occur. Therefore, a phase change will occur when a vial of 10 mL of water is placed into a cup of crushed ice mixed with four spoonfuls with 5 mL of sodium chloride for 30 minutes. If 10 mL of water is placed in an ice bath, it will then freeze at 5 degrees Celsius because the kinetic energy will leave quicker with the ice involved. The purpose of this lab is to observe what temperature the water must be to undergo a phase change.
Specific heat capacity of aqueous solution (taken as water = 4.18 J.g-1.K-1). T = Temperature change (oK). We can thus determine the enthalpy changes of reaction 1 and reaction 2 using the mean (14) of the data obtained. Reaction 1: H = 50 x 4.18 x -2.12.
In a 100ml beaker 30mls of water was placed the temperature of the water was recorded. 1 teaspoon of Ammonium Nitrate was added to the water and stirred until dissolved. The temperature was then recorded again. This was to see the difference between the initial temperature and the final temperature.
My aim in this piece of work is to see the effect of temperature on the rate of a reaction in a solution of hydrochloric acid containing sodium thiosulphate.
The purpose of this lab was to explore hydrates when water is removed from a compound with heat. By heating the magnesium sulfate, the mass of the water can be determined as the difference between the original weight and the weight after being heated. Not only can the mass be determined but also the amount of moles, ratio of magnesium sulfate to water, experimental percent of water, theoretical percent of water, and etc.
Ammonium chloride caused the water to cool. This means that the Ammonium chloride drew energy from the water to help it dissolve. As a result of losing its energy, the water cooled down. Calcium chloride caused the water to warm up. This means that energy from the calcium chloride was released and the water absorbed this heat. As a result, the temperature of the water increased.
Conclusion This experiment was set out to find the effect of different temperatures of hydrochloric acid on the rate of reaction with magnesium. The information recorded was then interpreted and compared to the hypothesis. From this information, a conclusion can be made to show that the rate of reaction relates to temperature in the reaction between hydrochloric acid and magnesium. In conclusion, as proven in this experiment, the higher the temperature of hydrochloric acid, the faster the reaction it has with magnesium.
In this experiment the Sodium Hydroxide solution went through three different phases where its quality and quantity changed. The first phase was called I. Preparing Approximately 0.1M NaOH, 1000mL of clear distilled water was boiled and then chilled to room temp.