Germain Henri Hess (August 7‚ 1802–November 30‚ 1850) was a Swiss-born Russian chemist and doctor who formulated Hess’s Law‚ an early principle of thermochemistry. Born in Geneva‚ Switzerland‚ his father was an artist and in 1805 moved the family to Russia to find work. Beginning in 1822‚ Hess studied medicine at the University of Tartu. He qualified as a physician in 1825. Hess turned to chemistry after a meeting with Jöns Jakob Berzelius‚ the famous Swedish chemist‚ and went to Stockholm University
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elements and compounds of which they are comprised. However‚ it can be difficult to derive the exact enthalpy in a reaction when multiple processes occur simultaneously. A method to circumvent this problem is outlined in Hess’s Law which was established in 1840. Hess’s Law states that the steps taken to determine the enthalpy of a reaction do not matter because the end results will be the same. This is the principle used for both parts of this experiment. In Part I of the experiment‚ two different
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CALCULATIONS Determining the amount Limiting Reagent used. nlimiting reagent = Molarity x Volume or Mass / Molar Mass Example: Limiting reagent is 5mL of 1.0 M HCl nlimiting reagent = Molarity x Volume nlimiting reagent = (1.0 [mol/L]) x 0.005 [L]) = 0.005 mol Determining the qrxn and qcal. qrxn + qcal = 0 -qrxn = qcal qrxn = ΔHrxn x nlimiting reagent qcal = Ccal ΔT qrxn = - Ccal ΔT + mcsolid ΔT (note: only if there is a precipitate formed in the reaction)
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Data and Observations: Part I Table: Metal: | Aluminum | Zinc | Iron | Copper | Mass of metal: | 27.776 g | 41.664 g | 34.720 g | 41.664 g | Volume of water in the calorimeter: | 26.0 mL | 26.0 mL | 26.0 mL | 26.0 mL | Initial temperature of water in calorimeter: | 25.3 °C | 25.3 °C | 25.3 °C | 25.3 °C | Temperature of hot water and metal in hot water bath: | 100.5 °C | 100.5 °C | 100.5 °C | 100.5 °C | Final temperature reached in the calorimeter: | 38.9 °C | 34.8 °C | 34.2 °C | 34
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409 Lab 40: Calorimetry Calorimetry is the measurement of the quantity of heat exchanged during chemical reactions or physical changes. For example‚ if the energy from an exothermic chemical reaction is absorbed in a container of water‚ the change in temperature of the water provides a measure of the amount of heat added. Calorimetry involves the use of a calorimeter. In this activity you will learn how the energy change in a physical change can be measured using a calorimeter. •
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Experiment 1 Calorimetry Chem 17 Univerity of the Philippines Diliman Discussion All chemical reactions involve energy. By understanding the behavior and connection of energy flow within a chemical reaction‚ we can understand and manipulate them to our advantage. The most common form of energy observed during chemical reactions is heat. The reaction may absorb (endothermic) or release (exothermic) heat‚ depending on the reacting substances. Calorimetry is the process of measuring the heat flow
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Calorimetry Lab Report Waris Butt PHY 112 Mr. Fasciano Class #18336 06/08/14 Purpose: Heat flow will occur between objects in contact until no more heat flow is detectable. Using calorimetry to analyze heat flow quantitatively and the equation: Q = mc ΔT‚ to determine the specific heat capacity of an object and heat flow from or to an object; respectively. Materials: Circle K 44 oz Styrofoam cup with lid Large Plastic
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First‚ the buffer was prepared by using the formula as follows: Figure 1: Calculation for prepare 0.1 M potassium phosphate buffer at pH 6 3.4007g of potassium phosphate was weighed and placed in 300 mL beaker. Then‚ 125 mL of water was added into the beaker that contained potassium phosphate. The mixture was dissolved using the stirring rod‚ and then the magnetic stirring bar was placed in the beaker for further dissolve when measuring the pH. The pH meter was used to measure the solution
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1. Determining the concentration of KMnO4 from the solution created by the stockroom. 16H+ + 2MnO4- (aq) + 5C2O42- (aq) → 2Mn2+ (aq) + 10CO2 (g) + 8H2O (l) Volume of potassium manganate (KMnO4) = 32.5 mL Mass of Sodium Oxalate (NaC2O4): 0.104 [KMnO4] Calculation: = (0.104g of NaC2O4)(1 mol NaC2O4 /134.0g)(2 mol KMnO4 / 5 mol NaC2O4)(1/32.5 mL)(1000 mL /1L) = 0.00955 M KMnO4 2. Using the standardized concentration of KMnO4 calculated above to find the mass percentage of the oxalate ion Equation:
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------------------------------------------------- ------------------------------------------------- Mapua Institute of Technology ------------------------------------------------- School of Mechanical and Manufacturing Engineering ------------------------------------------------- ------------------------------------------------- ------------------------------------------------- PHYSICAL STUDY NO.2 ------------------------------------------------- -------------------------------------------------
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