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Chemistry E18-2019 CH13 Summary and Test

This course covers various topics in chemistry including concentrations, pH, periodic table, bonding, stoichiometry, thermodynamics, and electrochemistry. The summary and test provide key concepts and examples.

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Chemistry E18-2019 CH13 Summary and Test

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  1. This course is approximately at this level CHEMISTRYE182019 CH13 SUMMARYand test Rudolf Žitný, Ústav procesní a zpracovatelské techniky ČVUT FS 2010

  2. SUMMARY and test CH13 Written test consists in 8 questions and one example. Each question represents 8 points, numerical example 16 points. Taken together, maximum from the written test is 80 points. Oral part (discussion of laboratory protocols, and written test) is 20 points. Rating

  3. 1. Units, constants… CH13 mass mkg 1 lb=0.45 kg length Lm 1 ft=0.3 m temperature TK,oC oF=1.8 oC+32, K=C+273.15 internal energy UJ 1 BTU=1 kJ mole = 6.02 x 1023 (Avogadro's number) R = 8.314 kJ/(kmol.K) (Universal gas constant) MH=1 g/mole, MC=12 g/mole, MN=14 g/mole, MO=16 g/mole Atmospheric pressure p=1.03·105 Pa Reference temperature T=298K Water: Density =1000 kg/m3, cp=4.2 kJ/(kg.K), hLG=2200 kJ/kg, Tc=3740C Air: Density =1.2 kg/m3, cp=1 kJ/(kg.K),

  4. 1. Concentrations… CH13 Mass concentration Molar concentration Molality Mass fraction Molar fraction

  5. 1. Units, concentrations… CH13 Example: Calculate mass fraction of oxygen in air assuming volumetric composition of air 21:79 (MO=16, MN=14).

  6. 2. periodic table,pH, polar/covalent bonds, CH13 the column 1 contains alkali metals, which have one more electron than the corresponding noble gases Non-metalsMissing electrons the column 18 contains noble gases which are inert . . MetalsSuperfluous electrons Covalent bond CH4(shared pairs) H has 1 electron in valence, C has 4 electrons in valence hydrogen needs 1 more electron to complete the valence (s-sublevel) carbon has only 4 electrons in valence shell and needs 4 more. 4 pairs of shared electrons complete valences of H, C Ionic bond NaCl (electrostatic attraction ions) Na-1 electron in valence, Cl-1 missing electron in valence sodium lends 1 electron chlorine borrows this electron (will have the same valence shell as stable Ar) Na+cationCl-anion (negative charge)

  7. 2. pH, polar/covalent bonds, periodic table CH13 Number of free protons H+ in 1 l of water [H+] is related to pH value pH = - log [H+] pH < 7 acids(concentration of free protons > 10-7 mol/l) pH >7 bases(concentration of free protons < 10-7 mol/l) - log [H+][OH-]=14

  8. 2- O O S O O 2. pH, polar/covalent bonds CH13 • How to derive the Lewis formula, given a chemical formula(and charge of ion). • Draw a possible structure(s) • Calculate total number of valence electrons (– charge of ion in case of ions) • Try to distribute these electrons so that all elements fill their valence shell (octet rule). • Carbon dioxide CO2 Sulfate (SO4)2- • (4+2x6)=16 electrons (8 pairs) (6+4x6) + 2=32 electrons (16 pairs) . O = C = O O - C - O because there is 10 pairs

  9. 2. pH, polar/covalent bonds CH13 Example: Hydrochlorid acid has pH=2. Calculate mass of HCl in 1 l of electrolyte. Solution: HCl + H2O → H+ + Cl- + H+ + OH- 14 =-log[H+]-log[OH-]=2- log[OH-] → [OH-]=10-12 Decomposed H2O Decomposed HCl Universal constant Total amount of H+ negligible Amount of free protons decomposed from HCl is 10-2-10-12 /l MHCl=36.5 g/mol, for molar concentration 10-2 mass of HCl is 0.365 g

  10. 3. stoichiometry CH13 Stoichiometric coefficients are negative for reactants and positive for products Stoichiometric coefficients are calculated by balancing all elements (each element represents one homogeneous algebraic equation for i)

  11. 3. stoichiometry CH13 Example: Calculate kg of water that is produced by burning 2 kg of methane.

  12. 4. Enthalpy, entropy, Gibbs energy CH13 First law of thermopdynamics δq = du + δw Internal energy du = cv dT Enthalpy dh = cp dT h=u+pv Entropy ds = (du+pdv)/T=dq/T Gibbs energy g=h-Ts

  13. 4. Enthalpy, entropy, Gibbs energy CH13 Hess law The enthalpy change of the reaction is a function of state and is independent of any intermediate reaction. Standard enthalpy of formation Enthalpy change of a chemical reaction Negative-exothermic, Positive-endothermic reaction Gibbs energy change of a chemical reaction Negative-feasible reaction

  14. 4. Enthalpy, entropy, Gibbs energy CH13 Example: Write definition of specific entropy. Calculate specific entropy change corresponding to temperature increase of water from 20 to 1000C assuming constant specific heat capacity of H2O (l) – you should know this value.

  15. p L-liquid S-solid G-gas T 5. State and phase equations CH13 Antoine VdW Clausius Clapeyron

  16. 5. State and phase equations CH13 Multiphase and multicomponent equilibrium Raoult´s law Henry’s law

  17. 5. State and phase equations CH13 Example What is the correct formulation of Raoult's law? a) pa/pa"=ya b) pa/p =ya c) pa/p =xa d) pa/pa"=xa

  18. 6. Electrochemistry, Reactions CH13 Oxidation ANODE Anode of galvanic cell is dissolved Reduction CATHODE

  19. 6. Electrochemistry, Reactions CH13 Or how to calculate concentrations of all participating species knowing only one scalar variable REACTION PROGRESS 

  20. 6. Electrochemistry, Reactions CH13 REACTION RATE Activation energy A  B + C A + B  C

  21. 6. Electrochemistry, Reactions CH13 Reversible REACTION Equilibrium constant (in terms partial pressures and concentrations) Equilibrium constant (as a function of temperature and Gibbs energy)

  22. 6. Reactions CH13 Example: If you combine potassium and chlorine in a galvanic cell, what will be anode? Estimate resulting voltage of this cell. Table of reduction potentials will be given as a part of problem setting Example: Reaction rate increased 2 times, when reaction temperature was increased from 10000C to 12000C. Calculate activation energy of the reaction.

  23. 7. Organic chemistry CH13 Derived alkylgroups -R • ALKANES linear chains containing single bonds • ALKENES linear chains containing at least one double bond • ALKYNES linear chains containing at least one triple bond • AROMATICring structure with alternating single and double bonds Derived aryl groups -R

  24. 7. Organic chemistry CH13 functional group derived from alkanes -CH3 (methyl), -C2H5 (ethyl), -C3H7 (propyl), … (alkyl groups) -OH (hydroxyl group /alcohols/), -COOH (carboxyl group /acids/), -NH2 (amines), -CONH2 (amides). Connecting functional groups -O- (ethers), R-CO-R (ketones, carbonyl group), R-CO-H (aldehydes) -COO-(esters /fats/).

  25. O CH3CH2-C-H 7. Organic chemistry CH13 Example: Classify and name the following compound Solution: ethylaldehyde

  26. 8. Polymers, Biochemistry CH13 Can be anything, for example amyl or aryl groups, halogens Polyolefines Polyamides

  27. H C C R O H H N O H Nucleic acids DNA RNA 8. Polymers, Biochemistry CH13 Biomolecules - polymers (except lipids) Lipids Carbohydrates Proteins e.g.Starch Cellulose e.g.Fats Amino acids (CH2O)6n C6H12O6 fructose, glucose

  28. 8. Polymers, Biochemistry CH13 Example: What is polyethylene (write formula)? Example: Classify starch and cellulose (what is it: protein, carbohydrate, lipid, or acid?). Describe differences.

  29. Final example CH13 Reaction enthalpy, spontaneity of chemical reaction (temperature range), equilibrium constant Given data from the following table, calculate maximum of what can be said about the chemical reaction: fermentation of ethylalcohol

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