Week 5 notes
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This 3 page Class Notes was uploaded by Moira Notetaker on Sunday February 7, 2016. The Class Notes belongs to CHM2045 at University of Florida taught by George Gower in Fall 2016. Since its upload, it has received 25 views. For similar materials see Chemistry 1 in Chemistry at University of Florida.
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Date Created: 02/07/16
CHM2045 Gower 2-1-16 Gas Forming Aqueous Reactions Carbonates(bases) mixed with acids o CaCO (s3+2HCl(aq) → CaCl 2aq)+H O(2)+CO (g) 2 Metal reacting with water or acids—depends on metal o Ca(s)+2H O(2) → Ca(OH) (2q)+H (g2 Determine the purity of sodium thiosulfate(Na S O :2128.3g/mol)if an aqueous amount containing 5.00g of sodium thiosulfate is titrated by 31.46mL of 0.5M standard I 2olution. What is the percent purity(by mass) of the sodium thiosulfate? 2- → 2- I2(s)+2S 2 (3q) 2I(aq)+S O4(6q) 0.03146L x (0.5 mol/1 L I ) 2 (2 mol S O /2 3ol I ) x2(1 mol Na S O 21 2o3 S2O 3 x (158.1g/ 1 mol Na S 2 )2=3rams of pure sodium thiosulfate (grams of pure sodium thiosulfate/5.00g) x 100% = percent purity FOR EXAM STUDY: Molarity and solutions Avogadro’s number Limiting reactant and yield Bronsted-Lowry acid-base Strong Acids Titration Nomenclature Stoichiometry Hydrates Net ionic equations CHM2045 Gower 2-4-16 Thermodynamics Entropy (Favorable vs. Unfavorable) o Exothemic process- any process in which thermal energy is transferred from the system to the surroundings System- thing doing the action(requiring energy) Exothermic rxns- kinetic energy becomes potential energy H2O(l) → H2O(s)+ energy o Endothermic process- system absorbs energy from surroundings Endothermic rxn- potential energy becomes kinetic → H2O(s)+energy H2O(l) o Enthalpy change( ∆ H¿ -used to quantify the heat(thermal energy transfer) into or out of a system in a process that occurs at a constant pressure ∆ H ( )- heat given off/absorbed during reaction at a constant pressure o ∆ H=∆E+P ∆V (work) ∆ E- change in energy P∆V -work that happens when gases are produced Thermal energy transfer(heat) is in units of Joules(J) or kilojoules(kJ) where 2 2 standard unit for Joule is [(kg x m )/s ] o If reaction is endothermic, ∆ H will be positive, greater than zero o If reaction is exothermic, ∆ H will be negative, less than zero For water: 6.01kJ are absorbed for every one mole of ice that melts at 0 ° C and at 1 atm Thermochemical equations The stoichiometric coefficients always refer to the number of moles in a substance ∆ If you multiply both sides of the equation by a factor n then H must also change by n What is the enthalpy change associated with melting 50.0g of ice? 50.0g H 2 x (1 mol H 2/18.014g) x (6.01 kJ/1 mol H O2 = 16.7 kJ What is the enthalpy change associated with freezing 50.0g of H O2 50.0g H 2 x (1 mol H 2/18.014g) x (-6.01 kJ/1 mol H 2) = -16.7 kJ Physical state of all reactions and products must be specified in thermochemical equations o H O(s) → H O(l) ∆ H=6.01kJ 2 2 → ∆ H=−6.01kJ o H 2(l) H2O(s)
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