Post Lab 3- Experiment 3

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University of New Mexico, Main Campus *

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1215L

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Chemistry

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May 5, 2024

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docx

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Date: 07/10/2023 Amaya Strauss CHEM 1215L-011 Experiment 3: Determination of Enthalpy for a Reaction Using Calorimetry Partner Names: Jackie Crump, Jana Valdez Deangelo & Martha Patterson
Data Analysis Example Calculation of Enthalpy: Equation: ΔHrxn = Σ ΔHproducts – Σ ΔHreactants Example: HSO4^-(aq) SO4^2- (aq) + H(aq) ΔH of HSO4^- = -885.75 kJ/mol (as per lab manual) ΔH of SO4^2- = -907.51 kJ/mol (as per lab manual) ΔH of H= 0 ΔHrxn = Σ ΔHproducts – Σ ΔHreactants ΔHrxn = -907.51 + 0 – (–885.75) ΔHrxn = –21.76 kJ/mol (–) indicates exothermic reaction Example Of Finding Standard deviation: Equation for Standard Deviation : x = recorded data points = mean of data points n = number of data points Example: Find the standard deviation for data points with average densities of 1.36, 1.6, and 1.54 g/ml. x= 1.36, 1.54, 1.60 =1.5 n=3 = 0.12489996 or 0.125 g/ml Equation for Percent Error: Percent error = (experimental – true/true) x 100 Error Analysis: Below are the calculated means and standard deviations for trials 1-4 for HCL and NaHSO4. In order to find these values, the change in temperature of each trial were used. Change in temperature can be calculated using the equation: ΔH= Temperature (final) -Temperature (initial)
Below are the calculated enthalpies( ΔH) in kJ/mol for each reaction of HCl/NaOH and NaHSO4/NaOH using mean values calculated above. These values were calculated using several values/eqns, such as: Cs of water= 4.18 J/g*k as per lab manual Mean temperature changes for HCl and NaHSO4 Total volume of rxn (20ml base & 21 acid)=41mL or 41g Qrxn= - Qcal Additionally, in order to determine the percent errors for these reactions, the following calculations were made in order to find the true value of the experiment. The values of ΔH for each product/reactant can be found in the lab manual on page 105 (109 pdf). The calculations can be seen below:
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