Stoichiometry Laboratory Report for General Chemistry | CHEM 1045, Lab Reports of Chemistry

Download Stoichiometry Laboratory Report for General Chemistry | CHEM 1045 and more Lab Reports Chemistry in PDF only on Docsity! Date Performed: 10/16/08 Name: Jen Williams Date Submitted: 10/23/08 Partner: Helia Zarkhosh Instructor: Giovanna Grandinetti Stoichiometry Objective: The objective of this lab is to find out the set of proportions between the numbers of moles of reactants consumed and products formed in the reaction between NaClO and KI. Data: Temperature of 131. mL NaClO solution: 20.52°C Temperature of 250. mL KI solution (16.6g solid): 20.64°C Vol. NaClO (in mL) 45 40 35 30 25 20 15 10 5 Vol. KI (in mL) 5 10 15 20 25 30 35 40 45 Temperatur e (in °C) 24.81 28.90 29.06 28.33 26.91 26.09 24.91 24.05 22.99 Sample Calculations: Amount of NaClO required: (0.762 M)(x) = (0.400 M)(250. mL) x= 131. mL NaClO Amount of KI required: (0.400 M)(250. mL)/x = 0.100 (0.100)[(166 g/mol)/x] 16.6 g KI Initial temperature: (20.52°C)(131 mL NaClO)+(20.64°C)(250 mL KI) =20.60°C Mole fraction of NaClO: (45 mL NaClO)/(45 mL NaClO + 5 mL KI) =0.9 Results and Conclusions: In this lab, students found the maximum heat release of the reaction that occurs between NaClO and KI in an aqueous solution. Through the method of stoichiometry, students were able to yield an initial temperature of each solution and the mole fraction for all the experiments. This was seen as the amount of KI and NaClO were decreased by 5 mL and increased by 5 mL, respectively, after each trial. After all trials, it was determined that the maximum heat release occurred at .70 mole fraction of NaClO. The chart below illustrates the different results of the lab after calculations were taken into account. Mole fraction of NaClO Volume KI (mL) Volume NaClO (mL) Initial temperature (°C) Final temperature (°C) ΔTT (°C) 0.90 5 45 20.60 24.81 4.81 0.80 10 40 20.60 28.90 8.30 0.70 15 35 20.60 29.06 8.46 0.60 20 30 20.60 28.33 7.73 0.50 25 25 20.60 26.91 6.31 0.40 30 20 20.60 26.09 5.49 0.30 35 15 20.60 24.91 4.31 0.20 40 10 20.60 24.05 3.45 0.10 45 5 20.60 22.99 2.39 Discussion of Experimental Uncertainty Due to the measuring apparatus available in this lab, error was virtually inevitable for every group. Students had to obtain amounts greater than 25 mL of each solution throughout the trials with a 25 mL graduated cylinder. To do this, students had to measure an amount in the instrument, and then empty into the designated beaker. After that, the students had to measure in the same graduate and get the final amount whatever was needed. When this is done, not all of the fluid is emptied and the amounts aren’t exact in the appropriate beaker. Another common error occurred in groups when a person would measure the temperature of one of the chemicals and not put the MeasureNet probe in water before obtaining the temperature of the next solution. When this happens, the chemicals become mixed and the amount of the solution collected is diluted and not completely accurate. Also, some of the reaction already takes place which would reflect a temperature that was either too high or too low, depending. A last area of uncertainty that caused major errors is the fact that my lab partner and I did not take a new initial temperature of the NaClO and KI solutions before each final reading. This changes the change in temperature reading, and thus the entire graph is compromised. Answers to Definitions a. A stoichiometric coefficient is the number in front of a compound/element that represents the amount of moles that are present for it in a balanced chemical equation. b. A mole fraction is a proportional value of the amount of moles of a compound/element in a balanced chemical equation in comparison to another in the same equation. c. Molarity is the amount of moles in a solution divided by the amount of liters of the entire solution.