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## Enthalpy

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**Click on buttons to go forward or back**Question mark buttons go to answers Enthalpy By: Veronica Mendez and Quinn Shollenberger ONLY CLICK ON THE QUESTION MARKS AND/OR ARROW**Lost?**If at any time you are lost during the tutorial, right click and a menu should come up. Click on Go To Slide and select the slide you want or go back to the first slide.**Definition**• Enthalpy- the heat content of a system at constant pressure. • Enthalpy- ∆ H**Equation #1**• ∆H = nCp∆T • n is moles • Cp is specific heat capacity (usually a given value) • ∆T is the change in temperature**Equation #2**• ∆H =∑ ∆Hp - ∑ ∆Hr • ∑ ∆Hp is the summation of the products • ∑ ∆Hr is the summation of the reactants**Example problem**• Find ΔH of the reaction. • 1CH4 + 2O2 --> 1CO2 + 2H2O • Mole Ratio is 1:2:1:2 because the coefficient in front of CH4 is 1; coefficient in front of O2 is 2; coefficient in front of CO2 is 1; coefficient in front of H2O is 2.**Example problem: Set up**• ΔH = [∑(ΔHCO2 + ΔHH2O)] – [∑(ΔHCH4 + ΔHO2)]**Example Problem: Plugging in the numbers**• ΔH = [(-393.5KJ/m X 1m) + (-286KJ/m X 2m)] – [(-74.8KJ/m X 1m) + 0][(-393.5 KJ) + (-572 KJ)] –(-74.8 KJ) • ΔH = -890.7 KJ (exothermic)**Example Problem: Further explanations**• The numbers from the equation: ΔH = [(-393.5KJ/m X 1m) + (-286KJ/m X 2m)] – [(-74.8KJ/m X 1m) + 0][(-393.5 KJ) + (-572 KJ)] –(-74.8 KJ) can be found on any Chemistry reference source. This includes CP values.**Reminder**• Do not forget to cross out your moles • Be careful with positive and negative signs**Quiz question 1**• Calculate ΔH at 25°C for: Na2O (s) + H2O (g) NaOH (s)**Quiz question 2**• If 15.0 g of Gold is heated from 16.1°C to 49.3°C, what is the heat absorbed by the gold?**Quiz question 3**• When 4.4 Kg of NaCl cools from 67.2°C to 25.0°C, how much heat is gained by the surroundings from the NaCl? (Cp NaCl 50.5 J°C-1M-1)**Quiz Question 4**• Determine the standard molar heat of combustion (ΔH ) id Methanol, CH3OH, when it is burned. Use H20(g)**Explanation to Quiz question 1**• Steps: • Balance equation: Na2O+H2O 2NaOH • [(- 427KJ/m)(2m)]-[(242KJ/m)(1m) + (- 415.9KJ/m)(1m)] • ΔH = -196.1KJ**Explanation to Quiz question 2**• ∆H = nCp∆T • 15.0 g(1m/ 197g)= 0.07614m • (0.07614m)(25.4J/m°C)(33.2°C) • ∆H = 64.2 J**Explanation to Quiz Question 3**• ∆H = nCp∆T • Convert kg into g • 4400 g (1m/58.5g) = 75.2m • (75.2m)(50.5J/m°C)(42.2 °C) • ∆H = 1.60 x 10 J**Explanation to Quiz question 4**• Combustion reaction and balance the equation 2CH3OH + 3O2 2CO2 + 4H2O**Explanation for Quiz question 4 cont…**• [(-393.5KJ/m)(2m)+(242KJ/m)(4m)] – [0+(-239KJ/m)(2m)] • ∆H = 1277 KJ