CHEM MISC Activity B.3 Relationships in Acid-Base Reactions Lab Report, Lab Reports of Chemistry

Download CHEM MISC Activity B.3 Relationships in Acid-Base Reactions Lab Report and more Lab Reports Chemistry in PDF only on Docsity! Activity B.3 Relationships in Acid-Base Reactions Lab Report Collective Analysis A variable is a property of an object that can take on different values. The relationships between four variables were explored in experiments A (Part I) and B (Part II). The variables were VHCl (volume of hydrochloric acid), NNaOH (total number of drops of sodium hydroxide) and VH2O (volume of water), and T (temperature change). Variables can be categorized into different classes; this provides a structure to the data set that can help you to identify patterns (i.e., relationships between the values of two or more variables). In the sciences, experiments are designed to explore relationships between independent and dependent variables. 1. Identify the independent variable and dependent variable in Experiment A. Type of Variable Variable Name Experiment A Independent Variable Volume of HCl Dependent Variable Number of NaOH drops 1a) Briefly explain the reasons why you identified the variables above as independent or dependent. The volume of HCl is the variable that is being manipulated to observe the amount of NaoH required to neutralize the solution, therefore the volume of HCl, the independent variable, determines the amount of NaOH drops, the dependent variable, required to balance pH 1b) Describe the relationship between the independent and dependent variable in Experiment A. The independent variable, volume of HCl, determines the amount of NaOH drops, the dependent variable, required to neutralize the solution 1c). Consider experiment A in which the variable VH2O changed values between test tubes containing the same VHCl (e.g., between test tubes A1 and A2). Was the relationship between the two variables VHCl and NNaOH affected by the variable VH2O? Support your reasoning using data from the group file as evidence. [Hint: you may want to calculate average values of the dependent variable for each value of VH2O] The variable VH2O had no effect on the relationship between the two variables VHCl and NNaOH. The ratio between VHCl and NNaOH remained constant. While some variation did occur, it was statistically nonsignificant 2 2. Identify the independent variable and dependent variable in experiment B. Describe the relationship between these two variables. Type of Variable Variable Name Experiment B Independent Variable Volume of NaOH Dependent Variable Solution Temperature 2a) Briefly explain the reasons why you identified the variables above as independent or dependent. The volume of NaOH is the variable that is being manipulated to observe the change in temperature of the solution, therefore the volume of NaOH, the independent variable, determines the temperature, the dependent variable, of the solution. 2b) Describe the relationship between the independent and dependent variable in Experiment B. The independent variable, volume of NaOH, determines the temperature, the dependent variable, of the solution 2c) Consider Experiment B in which the variable VH2O changed values between test tubes having the same VNaOH (e.g, between test tubes B3 and B4). Was the relationship between the two variables NNaOH and T affected by the variable VH2O? Support your reasoning using data from the group file as evidence. [Hint: you may want to calculate average values of the dependent variable for each value of VH2O] The variable VH2O had an effect on the relationship between the two variables VNaOH and T. As VH2O increased, the difference in initial and final temperature of the solution increased. In B3 VH2O is 1.0mL and the average difference in temperature is 3.6 C. In B5 VH2O is 3.4mL and the average difference in temperature is 5.5 C. 3. Two chemical systems, interaction between hydrochloric acid and sodium hydroxide and the interaction between hydrochloric acid and potassium hydroxide, were investigated. Use the collection of data from the group file to plot volume of base (y-axis) versus volume of hydrochloric acid (x-axis) data from both systems. Use different markers to identify the different systems. 3b) How would the value of the slope of the trend line in the previous question change if the concentration of the hydrochloric acid was increased? Explain your reasoning. The slope is positive indicating an increasing relationship. The graph shows the volume of NaOH increases as the concentration of hydrochloric acid increases. The relationship is linear indicating a directly proportional relationship. If concentration of hydrochloric acid is increased slope will increase. 3c) How would the value of the slope of the trend line change if the concentration of base (sodium hydroxide or potassium hydroxide) was increased? Explain your reasoning. If the concentration of base were to increase, the amount of base required to neutralize the solution would decrease. This would lead to a decrease in slope due to the formerly mentioned. 3d). Use the drawing tools in MicroSoft Word to sketch a line in each set of axes below that illustrates the patterns between moles of acid and moles of base for each chemical system. What is the numerical value of the slope (i.e., the proportionality constant) in the equations for these graphs? Explain your reasoning. m = 1 Explanation The graph would be linear with a slope of 1 because the relationship between VHCl and NNaOH is linear and the molar ratio directly proportional. The equation would show as follows: HCl(aq) + NaOH(aq)-> H2O(l) +NaCl(aq) Amount of Hydrochloric Acid (moles) 4 A m ou nt o f S od iu m H yd ro xi de (m ol es ) m = 1 Amount of Hydrochloric Acid (moles) 4. Determination of Concentration of Base from Titration Data Part III Complete the table below using data that you personally collected for two volumes of HCl in Act B3 Part III. Identify the base as sodium hydroxide or potassium hydroxide. Assume that the concentration of HCl solution is 0.100 M. 4a) Concentration of Base Base Used: potassium hydroxide Trial 1 Trial 2 Trial 3 Volume HCl (+/- 0.01 mL) 5.00mL 5.00mL 5.00mL Initial Vol Base (+/-0.01 mL) 2.30mL 3.40mL 3.55mL Final Vol Base (+/- 0.01 mL) 7.30mL 8.40mL 8.55mL Volume of Base at Equivalence (+/- 0.02 mL) 2.00mL 3.70mL 3.80mL Concentration of Base (M) 0.135M 0.135M 0.132M Average Concentration of 0.134M Explanation The graph would be linear with a slope of 1 because the relationship between VHCl and NKOH is linear and the molar ratio is directly proportional. The equation would show as follows: HCl(aq) + KOH(aq) -> H2O(l) +KCl(aq) A m ou nt o f P ot as si um H yd ro xi de (m ol es ) 5