Chem 102 Lab-1

Chem 102 Lab-1 - Karthik Gopavaram CHEM 112-202 January 29,...

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Karthik Gopavaram CHEM 112-202 January 29, 2008 - Exp. 5 - Thermochemistry and Calorimetric Measurements Abstract
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The experiment will explore Hess's Law, specific heat, heat capacity and other thermodynamic principles. A calorimeter will be calibrated. The specific heat and atomic weight of a metal will be calculated. The heat of solution will be determined and the heat of reaction using magnesium, magnesium oxide and Hydrochloric acid. The experiment will be considered a success if the atomic weight of the metal, heat of solution, and enthalpy of reaction are within 10% of the accepted values. Experimental Stoichiometric Equations: Mg (s) + 2 H + (aq) --- > Mg 2+ (aq) + H 2 (g) H rxn 1 2 H 2 (g) + O 2 (g) --- > 2 H 2 O (l) H rxn 2 Mg 2+ (aq) + H 2 O (l) --- > MgO (s) + 2H + (aq) H rxn 3 4 Mg (s) + 2 O 2 (g) --- > 4  MgO (s) H f = H rxn 1 + H rxn 2 + H rxn 3 Mathematical Formulas: H = H final - H inital q = m * s * T C = m * s -q metal = q water +q calorimeter = q total -m m* s m* T = m w* s w * T + m c* s c* T = q total H solution = U + H h = q (water) + q (salt) + q (calorimeter) H sol = m w* s w* T +C c* T H o = S (bonds in reactants) - S (bonds in products) H f (MgO) = H rxn 1 + H rxn 2 - H rxn = H rxn 1 + H rxn 2 + H rxn 3 T c = T max - T i T metal = T max - T hot Reagents: Common Name Formula Molecular Weight (g/mole) Molar Heat Capacity (J/(K * mole)) Water H 2 O 18.015 75.290 Hydrochloric Acid HCl 36.461 gas-29.12 Magnesium Mg 24.305 --- Magnesium Oxide MgO 40.304 37.150 Materials: -2 Styrofoam cups -lid -stir bar -2 thermometer -100 mL beaker -400 mL beaker -magnetic stirrer -ring stand
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-ring -Bunsen burner -test tube -stopper -sand paper Experimental Apparatus Procedure: Part A: 1. The calorimeter was constructed by placing one Styrofoam cup inside the other. 2. The stir bar and thermometer-stopper assembly were inserted through the lid and placed on the top cup. 3. The assembly was weighed and 40 mL of water added. 4. The temperature was observed and the assembly was reweighed. 5. The assembly was placed inside a 400 mL beaker atop a magnetic stirrer, held by an iron ring. 6. The thermometer was clamped so that the thermometer was suspended just above the bottom of the calorimeter.
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7. A 100 mL beaker was weighed, 40 mL of water added and reweighed. 8. The second thermometer was placed inside it and the beaker was heated. 9. With constant and gentle stirring, the temperature of the water in the calorimeter was recorded every 30
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Chem 102 Lab-1 - Karthik Gopavaram CHEM 112-202 January 29,...

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