* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download all practice examples
Gas chromatography wikipedia , lookup
Process chemistry wikipedia , lookup
Electrochemistry wikipedia , lookup
Water splitting wikipedia , lookup
Photoredox catalysis wikipedia , lookup
Marcus theory wikipedia , lookup
Chemical thermodynamics wikipedia , lookup
Hypervalent molecule wikipedia , lookup
Physical organic chemistry wikipedia , lookup
Stability constants of complexes wikipedia , lookup
IUPAC nomenclature of inorganic chemistry 2005 wikipedia , lookup
Click chemistry wikipedia , lookup
Rate equation wikipedia , lookup
Hydrogen-bond catalysis wikipedia , lookup
Electrolysis of water wikipedia , lookup
Chemical reaction wikipedia , lookup
Lewis acid catalysis wikipedia , lookup
Photosynthetic reaction centre wikipedia , lookup
Transition state theory wikipedia , lookup
Chemical equilibrium wikipedia , lookup
Quantitative Chemistry •matter •units •significant figures •atomic structure, isotopes, periodic table •basic nomenclature (ions, molecular &inorganic compounds) •stoichiometry and balancing equations by inspection •moles and Avogadro’s number •empirical and molecular formulae •limiting reagents 1 PRACTICE EXAMPLE A nugget of gold with a mass of 521 g is added to 50.0 mL of water. The water level rises to a volume of 77.0 mL. What is the density of the gold? 2 PRACTICE EXAMPLE Naturally occurring Mg has three isotopes: 24Mg (78.90 %) 23.9850 u 25Mg (10.00 % )24.9858 u 26Mg (11.10 %) 25.9826 u AAM=? 3 PRACTICE EXAMPLE NAME: NaCl K2SO4 Ba(OH)2 cobalt(II) nitrate silver sulfide ferric chloride 4 PRACTICE EXAMPLE Anion Corresponding acid ClS2ClO4ClO3ClO2ClO- 5 PRACTICE EXAMPLE NAME: SO2 PCl5 N2O3 NF3 P4S10 silicon tetrabromide 6 PRACTICE EXAMPLE BALANCE: C2H6 + O2 → CO2 + H2O Al + HCl → AlCl3 + H2 7 PRACTICE EXAMPLE How many oxygen atoms are in 1.50 mol of sodium carbonate? 8 PRACTICE EXAMPLE Determine the empirical formula of a compound with 10.4% C, 27.8% S and 61.8% Cl. 9 PRACTICE EXAMPLE Eucalyptol has an empirical formula of C10H18O. The experimentally determined molecular mass of this substance is 152 u. What is its molecular formula? 10 PRACTICE EXAMPLE Determine (i) which reactant is the limiting reactant and (ii) how much excess reactant is leftover in the following reaction: 3NH4NO3 + Na3PO4 → (NH4)3PO4 + 3NaNO3 30.0 g 50.0 g 11 PRACTICE EXAMPLE Determine the theoretical yield and the % yield of NaNO3 if 15.0 g of sodium nitrate is formed when the reaction is carried out. 3NH4NO3 + Na3PO4 → (NH4)3PO4 + 3NaNO3 30.0 g 50.0 g 12 TYPES OF REACTIONS • • • • • • • • Electrolytes Acid- base reactions Solubility rules Precipitation reactions Writing ionic equations Oxidation numbers Redox reactions Concentration 13 PRACTICE EXAMPLE BALANCE AND SHOW PHASES: BaCl2 + H2SO4 → BaSO4 + HCl 14 PRACTICE EXAMPLE BALANCE: H2SO4(aq) + NaOH(aq) → 15 PRACTICE EXAMPLES OXIDATION No OF BOLD: S2O32FeO42Na2SO3 S8 NH4+ 16 PRACTICE EXAMPLE BALANCE IN ACIDIC: Fe2+(aq) + MnO4¯ Fe3+(aq) + Mn2+(aq) 17 PRACTICE EXAMPLE BALANCE IN BASIC: S(s) + ClO¯(aq) SO32- (aq) + Cl¯(aq) 18 PRACTICE EXAMPLE Calculate the molarity of a solution made by dissolving 5.00 g of glucose, C6H12O6 , in sufficient water to form exactly 100. mL of solution. 19 PRACTICE EXAMPLE **How many grams of NaOH are needed to neutralise 20.0 cm3 of 0.150 M H2SO4 solution? 20 PRACTICE EXAMPLE How many millilitres of 5.00 M K2Cr2O7 solution must be diluted to prepare 250. cm3 of 0.100 M solution? 21 PRACTICE EXAMPLE What mass of Ag2CrO4 (331.8 g mol-1) will precipitate if excess K2CrO4(aq) is added to 514.6 mL of 0.1683 M AgNO3 . The unbalanced equation for the reaction is: AgNO3(aq) + K2CrO4(aq) → Ag2CrO4(s) + KNO3(aq) 22 PRACTICE EXAMPLE BALANCE AND SHOW PHASES: Ba(NO3)2 (aq) + Li2SO4 (aq) → 23 GASES • Properties of gases • Gas Laws • Gas equations – General gas equation – Ideal gas equation (density & molar mass derivation) – Partial pressures – Gas collected over water – Van der Waal’s real gas equation • Kinetic molecular theory of gases 24 PRACTICE EXAMPLES Convert: 253 Torr → atm 326 Pa → atm 51 atm → mmHg 65 atm → bar 25 PRACTICE EXAMPLE A gas bubble with a volume of 1.00 mm3 originates at the bottom of the lake where the pressure is 3.00 atm and the temperature is 12.5 0 C. Calculate its volume (in mm3) when the bubble reaches the surface of the lake where the pressure is 695 Torr and the temperature is 15 0C. 26 PRACTICE EXAMPLE Determine the molar mass and identity of a 0.134 g sample of gas with a volume 75.0 mL at STP? 27 PRACTICE EXAMPLE What is the density (in g dm-3) of a sample of Cl2 gas at 1124 Torr and 24 0C? 28 PRACTICE EXAMPLE A gaseous mixture made from 6.00 g O2 and 9.00 g CH4 is placed in a 15.0 L vessel at 0 °C. Calculate the partial pressure of each gas and the total pressure in the vessel (in Pa). 29 PRACTICE EXAMPLE A 31.46 mL sample of gas was collected over water at 296.9 K and at a pressure of 706.4 mmHg. Consider the gas sample to be a mixture of water vapour and N2 gas. What mass of nitrogen was collected? (Vapour pressure of water at 296.9 K is 22.3 mmHg) 30 PRACTICE EXAMPLE Calculate the pressure of 1.00 mol Cl2(g) confined to a volume of 3.00 dm3 at 0.0 C using the van der Waals equation. (Note a= 3.64 kPa dm6 mol-2, b = 0.0427 dm3 mol-1, R = 8.314 kPa dm3 mol-1 K-1) 31 ELECTRONIC STRUCTURE OF ATOMS • • • • • Wave nature of light Quantum theory Line spectra (Bohr model) Quantum numbers and atomic orbitals Electron configuration 32 PRACTICE EXAMPLE For radiation of wavelength 242.4 nm, what is the energy of one photon of light? 33 PRACTICE EXAMPLE Calculate the wavelength (in nm) associated with an electronic transition in the hydrogen atom from n=4 to n=1. 34 PRACTICE EXAMPLE Determine E for the transition of an electron from n=5 to n=2 in a hydrogen atom. 35 PRACTICE EXAMPLES Give the numerical values of n and l and ml corresponding to each of the following designations: i) 3p ii) 2s iii) 4f 36 PRACTICE EXAMPLE Write the expanded and condensed electron configuration of the following: i) N ii) Si iii) Cu 37 PRACTICE EXAMPLE Draw the electron “block” diagram of carbon and aluminium 38 BASICS OF BONDING • • • • • • • • Octet rule Ionic bonds and compounds Covalent bonds and compounds Polarity and Electronegativity Lewis symbols and structures Formal Charge Resonance structures Exceptions to Lewis Rules 39 PRACTICE EXAMPLES Draw Lewis symbols or structures for Calcium, silicon, neon, PCl3, CH3OH, N2, NH4+, OH- 40 PRACTICE EXAMPLE Draw three structures of CNS- with N as the central atom and decide with formal charge which is the best structure. 41 PRACTICE EXAMPLE Draw the resonance structures of O3 and NO3- 42 ELECTRON & MOLECULAR GEOMETRY • VSEPR • Electron geometries • Molecular geometries 43 PRACTICE EXAMPLES DETERMINE ELECTRON AND MOLECULAR GEOMETRY AND BOND ANGLE: PF4+ , AlCl63- , ICl3 , CH3+ 44 INTERMOLECULAR FORCES • Physical state • Inter- vs Intra• Types of IM forces – – – – – Dipole-dipole forces Hydrogen bonding Ion-ion forces Ion-dipole forces Van der Waal’s forces • Liquid properties 45 PRACTICE EXAMPLES Why does NH3 have a higher boiling point than CH4 ? Why does KCl have a higher melting point than I2 ? 46 PRACTICE EXAMPLE Arrange the following in order of increasing boiling points and identify the IM forces present in each compound: CH3OH, CO2, RbF, CH3Br 47 PRACTICE EXAMPLES INTERMOLECULARE FORCES PRESENT=? i. H2O ii. N2 iii. C6H5Cl iv. C6H6 THERMOCHEMISTRY • Energy – Heat – Heat capacity – Calorimetry • Enthalpy – Heat of formation – Heat of reaction – Bond energies 49 PRACTICE EXAMPLES A piece of titanium metal with a mass of 20.8 g is heated in boiling water to 99.5 °C and then dropped into a coffee-cup calorimeter containing 75.0 g of water at 21.7 °C. When thermal equilibrium is reached, the final temperature is 24.3 °C. Calculate the specific heat capacity of titanium. (Specific heat of water is 4.184 J g-1 K-1) 50 PRACTICE EXAMPLES A 50.0 g sample of water at 100 °C is poured into a 75.0 g sample of water at 25 °C. What will be the final temperature of the water? Specific heat capacity of water = 4.184 J g-1 °C-1 51 PRACTICE EXAMPLES A 0.1375 g piece of magnesium was burned in a bomb-calorimeter containing 300 .g of water. The temperature increased by 1.126 C. The heat capacity of the calorimeter is 1769 J C-1 and the specific heat capacity of water is 4.184 J g-1 C-1. Calculate the heat given off by the magnesium in J g-1. 52 PRACTICE EXAMPLES When 50.0 mL of 1.00 M NaOH is added to 100.0 mL of 0.500 M HCl in a coffee cup calorimeter at 25.8 C, the temperature rises to 34.8 C. Assume that the density of the solution is 1.00 g mL-1 and that its specific heat capacity is 4.184 J g-1 C-1. The equation for the reaction is: NaOH(aq) + HCl(aq) → NaCl(aq) + H2O(l) Calculate the enthalpy of the reaction in kJ mol-1 . 53 PRACTICE EXAMPLES Calculate Hrxn for the combustion of 1 mol of benzene (C6H6(l)) given that Hf for C6H6(l) ,CO2(g) and H2O(l) are 49.0 kJ/mol, -393.5 kJ/mol and -285.8 kJ/mol respectively. 54 PRACTICE EXAMPLES Find Hrxn for ½ N2(g) + O2(g) NO2(g) given that: ½N2(g) + ½O2(g) NO(g) H = 90.25 kJ 2NO2(g) 2NO(g) + O2(g) H= 114.14 kJ 55 PRACTICE EXAMPLES Use the table of bond energies shown below to calculate Hrxn for: C2H4(g) + HCl(g) C2H5Cl(g) Bond CC C=C CH HCl CCl Bond energy/kJ mol-1 348 614 413 431 328 56 REACTION KINETICS • • • • • • • Reaction rates Reaction order Reaction mechanisms Collision frequency Energy profile diagrams Arrhenius equation Catalysts 57 PRACTICE EXAMPLES (a)N2 + 3H2 2NH3 Rate = (b) H2O2 + 2H+ + 3I¯ I3¯ + 2H2O Rate = 58 PRACTICE EXAMPLE A + B products rate = k[A]m[B]n initial conc/mol dm–3 [A] [B] 0.10 0.10 0.20 0.10 0.30 0.10 0.30 0.20 0.30 0.30 initial rate/mol dm–3 s–1 0.20 0.40 0.60 2.40 5.40 1 2 3 4 5 CALCULATE m, n and k 59 PRACTICE EXAMPLE For the reaction: NO2(g) + CO(g) NO(g) + CO2(g) the variation of the initial rate with the initial concentration of NO2 (the initial concentration of CO kept constant), was found to be as follows: Experiment [NO2]/mol dm-3 Initial rate/mol dm-3 s-1 1 0.150 0.010 2 0.300 0.040 3 0.600 0.160 4 0.900 0.360 Deduce the order of the reaction with respect to NO2 60 PRACTICE EXAMPLE For the alkaline hydrolysis of ethyl nitrobenzoate (A) the following data were obtained at 25 C. Time/s 0 500 800 1500 2000 [A]/mol dm-3 0.0500 0.0167 0.0119 0.0071 0.0056 Evaluate the order of the reaction and calculate k t [A] t ln[A] t 1/[A] 0 0.05 0 -2.99573 0 20 500 0.0167 500 -4.09235 500 59.88024 800 0.0119 800 -4.43122 800 84.03361 1500 0.0071 1500 -4.94766 1500 140.8451 2000 0.0056 2000 -5.18499 2000 178.5714 61 SOLUTION 0.06 0 0 0.05 500 1000 1500 2000 2500 -1 -2 ln[A] 0.03 0.02 -3 -4 0.01 -5 0 0 500 1000 1500 2000 2500 -6 t/s t/s 1/[A] [A] 0.04 200 180 160 140 120 100 80 60 40 20 0 0 500 1000 1500 2000 2500 t/s 62 PRACTICE EXAMPLE For the reaction A products, the following data is given in the table below: [A]/M 0.600 0.497 0.413 0.344 0.285 0.198 0.094 Time/s 0 100 200 300 400 600 1000 A) Show that the reaction is first order by plotting the appropriate graph for first order reactions. B) What is the value of the rate constant, k? C) What is [A] at t = 750 s? 63 SOLUTION time/s time/s ln[A] 0 0 200 400 600 800 1000 -0.5 -1 ln[A] -1.5 -2 -2.5 y/x = (-2.36-(-0.51))/(1000-0) s= -1.85 x 10-3 s-1 1200 0 -0.51 100 -0.699 200 -0.884 300 -1.07 400 -1.26 600 -1.62 1000 -2.36 PRACTICE EXAMPLE A single step reversible reaction has an activation energy for the forward reaction (Ea,f) of 28.9 kJ and 41.8 kJ for the reverse reaction (Ea,r) Draw a potential energy level diagram and indicate H PRACTICE EXAMPLE The rate constant for the reaction: H2(g) + I2(g) 2HI(g) has been determined at the following temperatures: k/M-1 s-1 T/K 5.4 x 10-4 599 2.8 x 10-2 683 Calculate the activation energy, Ea, for the reaction in J mol-1. CHEMICAL EQUILIBRIUM • Dynamic Equilibrium • Equilibrium constant expression –Kc –Kp –Qc • Le Chatelier’s principle PRACTICE EXAMPLES EXPRESS KC a) 2 H2S(g) ⇌ 2 H2(g) + S2(g) b) PCl3(g) + 3 NH3(g) ⇌ P(NH2)3(g) + 3 HCl(g) c) Na2CO3(s) + SO2(g) + ½ O2(g) ⇌ Na2SO4(s) + CO2(g) PRACTICE EXAMPLE N2O(g) + ½ O2(g) ⇌ 2 NO(g) Kc = ? N2(g) + ½ O2(g) ⇌ N2O(g) Kc = 2.7 x 10-18 N2(g) + O2(g) ⇌ 2NO(g) Kc = 4.7 x 10-31 PRACTICE EXAMPLE A 5.00 L flask is filled with 1.86 mol NOBr. At equilibrium there is 0.082 mol Br2 present. Determine Kc for the reaction at 25 C. 2 NOBr(g) ⇌ 2 NO(g) + Br2(g) PRACTICE EXAMPLE A 0.0240 mol sample of N2O4(g) is allowed to come to equilibrium with NO2(g) in a 0.372 L flask at 25 C. Calculate the amount of N2O4(g) at equilibrium. N2O4(g) ⇌ 2 NO2(g) Kc = 4.61 x 10 -3 at 25 C PRACTICE EXAMPLE 2 NH3(g) ⇌ N2(g) + 3 H2(g) Kp = ? Kc = 2.8 x 10-9 at 298K PRACTICE EXAMPLE Is a mixture of 0.0205 mol NO2(g) and 0.750 mol N2O4(g) in a 5.25 L flask at 25 C at equilibrium? If not, in which direction will the reaction proceed? N2O4(g) ⇌ 2 NO2(g) Kc = 4.61 x 10-3 at 25 C PRACTICE EXAMPLE A mixture consisting of 0.150 mol H2 and 0.150 mol I2 is brought to equilibrium at 445 C in a 3.25 L flask. What are the equilibrium amounts of H2, I2 and HI? The equilibrium reaction is given below. H2(g) + I2(g) ⇌ 2HI(g) Kc = 50.2 at 445 C PRACTICE EXAMPLE (a) 4 HCl(g) + O2(g) ⇌ 2 H2O(g) + 2 Cl2(g) Effect on equilibrium and Kc? Addition of oxygen gas (b) An increase in temperature (c) Reduction of the volume of the reaction container (d) Addition of a catalyst (e) Removal of HCl(g) from the reaction vessel. ΔH = 28 kJ ACID-BASE EQUILIBRIA • Definition of acids and bases –Arrhenius –Brønsted-Lowry • Strong vs weak acids and bases • Self-ionization of water (Kw) • Ionisation constants (Ka, Kb) • pH, pOH PRACTICE EXAMPLES LABEL CONJUGATE ACID-BASE PAIRS: (a) HPO42- + NH4+ ⇌ NH3 + H2PO4¯ (b) SO42- + H2O ⇌ HSO4¯ + OH¯ PRACTICE EXAMPLE Calculate the pH of a 0.050 M nitrous acid (HNO2) solution. Ka = 4.5 x 10-4 PRACTICE EXAMPLE What is the pH of a 0.10 M solution of NH3? What is the % ionisation for this solution? Kb = 1.8 x 105 PRACTICE EXAMPLE Quinine is a naturally occurring base used to treat malaria. A 0.0015 mol dm-3 solution of quinine has a pH of 9.84. The basicity of quinine is due to the nitrogen atom that picks up a proton from water in the same manner as ammonia. a) Calculate Kb for quinine. b) Determine the degree of ionisation.