The Effect of Ion Dissociation on Boiling Point Elevation

Study Case The Effect of Ion Dissociation on Boiling Point Elevation: The Case of NaCl Solution vs. Non-electrolyte Solution Michael Kurniawan (2018123456) University of Cincinnati, 2600 Clifton Ave, Cincinnati, OH 45221, United States kurniaml@mail.uc.edu Abstract Boiling point elevation is a type of colligative property that arises due to the number of solute particles in a solution. The type of solution affects the magnitude of boiling point elevation, which in this study was compared between electrolyte solutions (salt, NaCl) and non-electrolyte solutions (sugar, C6H12O6). This study aims to identify the effect of these two types of solutions on boiling point elevation with a high degree of accuracy. The method used is quantitative, including the preparation of tools and materials, variation of substances, and measurement using a digital laboratory thermometer. The experimental data were analyzed to determine the relationship between the type of solution and boiling point elevation. The results of the study show a linear relationship in which the type of solution significantly affects the increase in boiling point. These findings provide practical value in understanding the phenomenon of boiling point elevation, which can be applied in various experimental activities and everyday life. Keywords: type of solution, boiling point, electrolyte, non-electrolyte, colligative properties. INTRODUCTION Every substance has mass and occupies space, composed of small particles that cannot be observed directly. The structure of these particles varies, determining the form and properties of the substance [1]. Physical properties such as boiling point, freezing point, and surface tension are influenced by the attractive forces between molecules [2]. In liquids, molecules can move past each other, and this difference in arrangement plays an important role in determining thermal properties, including boiling point elevation MICHAEL KURNIAWAN 1 Study Case [3]. A solution is defined as a homogeneous mixture consisting of molecules, atoms, or ions [4]. In a solution, the substance present in smaller quantities is called the solute, while the substance present in larger quantities is called the solvent [5]. The concentration of a solution, which is the ratio of the amount of solute to the amount of solvent, affects the boiling point because the boiling point is reached when the saturated vapor pressure is equal to atmospheric pressure [6]. The colligative properties of a solution depend on the number of solute particles, not on their chemical type. In electrolyte solutions, solutes dissociate into ions, so the number of particles increases compared to non-electrolyte solutions with the same concentration [7]. As a result, electrolyte solutions exhibit a greater boiling point elevation than non-electrolyte solutions [8]. Electrolyte solutions are divided into strong and weak electrolytes based on their ability to conduct electricity. Strong electrolyte solutions such as table salt (NaCl) conduct electricity well because the ions move freely, while non-electrolyte solutions such as sugar (C6H12O6) do not conduct electricity at all [9]. Water is a universal solvent that can dissolve various chemical compounds such as salt, sugar, acids, and certain gases [10]. When chemical compounds are dissolved in water, the properties of the solvent change, including an increase in boiling point, a decrease in freezing point, and osmotic pressure [11]. The higher the concentration of the solute, the higher the boiling point of the solution. Temperature describes the degree of heat or cold of an object. Heat energy flows from objects with high temperatures to objects with low temperatures [12]. This process explains that to boil a solution with a high concentration, more energy is needed for the water molecules to escape as vapor [13]. Therefore, understanding the colligative properties of solutions, especially the increase in boiling point, is important for experimental studies in applied chemistry at the University of Cincinnati. RESEARCH METHODOLOGY This study uses an experimental quantitative method because this method is capable of producing accurate numerical data and allows for objective analysis of the relationship between variables. The research process consists of four main stages: (1) preparation of tools and materials, (2) variation of solution types, (3) measurement, and MICHAEL KURNIAWAN 2 Study Case (4) data analysis. Preparation of Tools and Materials Preparation was carried out to ensure that the experimental data obtained was valid. The tools used included: three 100 mL beakers, a 100 mL measuring cup, a spatula, a hot plate, an analytical balance, a stirring rod, and a digital laboratory thermometer. The materials used consisted of pure water (distilled water), 1 M salt solution (NaCl), and 1 M sugar solution (C6H12O6), each in a quantity of 50 mL. A concentration of 1 M was chosen because it was able to show a significant difference in boiling point between the two types of solutions. Variations in Solution Types The solutions tested were divided into two categories: • Electrolyte solutions: NaCl, which can conduct electricity because it dissociates into Na⁺ and Cl⁻ ions. • Non-electrolyte solutions: C6H12O6, which does not dissociate into ions and therefore does not conduct electricity. Measurement The boiling point was measured carefully with a digital thermometer, parallel to the surface of the eye to avoid reading errors. Each solution was heated using a hot plate until it boiled, then the temperature was recorded as the boiling point of the solution. The molarity calculation formula used was: 𝑛 𝑀= 𝑉 where: • M= molarity (mol/L) • n= moles of solute (mol) • V= volume of solution (L) From these calculations, the mass of NaCl was found to be 5.85 grams in 100 mL of water, and the mass of C6H12O6 was 18 grams in 100 mL of water. Experiment Implementation The research was conducted at the University of Cincinnati Chemistry Laboratory in accordance with laboratory safety standards. Experimental steps: 1. Measure the room temperature using a thermometer. 2. Prepare and heat pure water to boiling point, then record the boiling point temperature. MICHAEL KURNIAWAN 3 Study Case 3. Heat the NaCl and C6H12O6 solutions separately, then measure the boiling point of each. 4. Compare the measurement results and record the data in the observation table. RESULTS AND DISCUSSION The results and discussion section consists of five subsections that describe the main aspects of the study, namely boiling point elevation, experimental results, data analysis, factors affecting boiling point elevation, and the relationship between solution type and boiling point elevation. Boiling Point Elevation Colligative properties are characteristics of solutions that depend on the number of solute particles (σ) regardless of their type or chemical properties [1]. There are four main colligative properties, namely: (1) vapor pressure lowering, (2) boiling point elevation, (3) freezing point depression, and (4) osmotic pressure. The boiling process occurs when the vapor pressure of a liquid is equal to the atmospheric pressure around it. Vapor bubbles begin to form from the bottom of the liquid and move to the surface. If the air pressure above the surface decreases (for example, due to local cooling), the boiling point of the liquid can drop [2]. The increase in the boiling point of a solution (ΔTb) is the difference between the boiling point of the solution and the boiling point of the pure solvent. The greater the number of solute particles, the more difficult it is for the solvent molecules to turn into vapor, so a higher temperature is required for the solution to boil. Thus, the boiling point elevation depends heavily on the type of solute and the concentration of solute particles [3]. Experimental Data Results Table 2. Experimental Results of the Effect of Solution Type on Boiling Point MICHAEL KURNIAWAN 4 Study Case The data shows that pure water has the lowest boiling point, while salt solution (electrolyte) has the highest boiling point, indicating a significant effect of solution type on boiling point elevation. Experimental Data Analysis From the observations, the boiling point of pure water is 78°C, sugar solution is 82°C, and salt solution is 84°C. The boiling point elevation is calculated using the following equation: Δ𝑇𝑏 = 𝑇𝑏∘ − 𝑇𝑏 (2) Explanation: ΔTb= boiling point elevation Tb∘= boiling point of the solution Tb= boiling point of the solvent [4] Thus, the boiling point elevation for the sugar solution is 4°C, while for the salt solution it is 6°C. Based on boiling time, pure water boils the fastest (17 minutes), followed by the sugar solution (20 minutes), and the salt solution (31 minutes). This shows that the higher the number of solute particles, the greater the heat energy required to reach the boiling point. Factors Affecting Boiling Point Elevation Several main factors affect boiling point elevation, including: 1. The concentration or number of moles of solute. The more solute particles there are, the greater the intermolecular forces that resist the phase change from liquid to gas [5]. 2. Solvent boiling point constant (Kb). This value depends on the type of solvent; water has Kb=0.512“ ” °C⋅kg/mol. 3. Air pressure. Higher atmospheric pressure will increase the boiling point, while low pressure will decrease it [6]. 4. Solvent type and heating. Gradual heating produces more stable data. In this study, a hot plate was used instead of an alcohol burner, so the boiling time was longer due to the lower heat transfer rate. For electrolyte solutions, the boiling point elevation is calculated using the dissociation coefficient (van't Hoff factor). The general formula for boiling point elevation is: Δ𝑇𝑏 = 𝐾𝑏 × 𝑚 × 𝑖 MICHAEL KURNIAWAN 5 (4) Study Case where: Kb= solvent boiling point elevation constant m= molality of solution i= van't Hoff factor The value of the van't Hoff factor (i) is calculated using: 𝑖 = 𝛼𝑛 + (1 − 𝛼) (5) where α= degree of dissociation, and n= number of ions resulting from dissociation. Relationship between Solution Type and Boiling Point Elevation Experimental data shows that the type of solution has a direct relationship with the boiling point elevation. Electrolyte solutions such as NaCl show a higher boiling point elevation than non-electrolyte solutions (sugar) and pure water. This is due to the ability of NaCl to dissociate into two ions (Na⁺ and Cl⁻), increasing the total number of particles in the solution [8]. Meanwhile, non-electrolyte solutions such as sugar do not undergo dissociation, so the number of dissolved particles is smaller. Theoretically, the greater the van't Hoff factor, the higher the boiling point elevation of a solution. This experiment also shows a small difference between the practical results and the theoretical value (100°C for pure water). This difference can be explained by laboratory conditions, the use of a hot plate with a slow heat rate, and room temperature affecting atmospheric pressure. Thus, the results of this experiment reinforce the theory that the boiling point of a solution is always higher than the boiling point of its pure solvent, because the presence of dissolved particles inhibits the evaporation of solvent molecules [9]. CONCLUSIONS Based on the results of experiments conducted at the University of Cincinnati Chemistry Laboratory, it can be concluded that the type of solution affects the boiling point elevation, although not extremely. Electrolyte solutions (NaCl) have a higher boiling point than non-electrolyte solutions (C6H12O6) and pure water. This is due to the greater number of ion particles in electrolyte solutions, which require more heat energy to boil. Thus, the higher the number of dissolved particles, the greater the increase in the boiling point of the solution. MICHAEL KURNIAWAN 6 Study Case REFERENCE MICHAEL KURNIAWAN 7