Chem Review Final Key

PART II-REVIEW FINAL EXAM-CHEM 111 Name: Key Last First 1. What is the net-ionic equation for the reaction that occurs when: a. nitrous acid and sodium hydroxide solutions are mixed.   HNO₂ + OH⁻ → NO₂⁻ + H₂O b. potassium hydroxide and hydrofluoric acid solutions are mixed. OH⁻ + HF → F⁻ + H₂O 2. Which of the elements given below will have: a. largest atomic size. Ba b. highest ionization potential Cl c. lowest electronegativity Ba d. lowest electron affinity Ba 3. a. Name the three classes of compounds that are considered as electrolytes.   1. Soluble salts 2. Strong acids 3. Strong bases b. Label each of the following as strong electrolyte, weak electrolyte, or non-electrolyte. (You must know the list of soluble salts, strong acids and strong bases to answer this question.)   i. NaC₂H₃O₂ strong ii. HC₂H₃O₂ weak iii. HCN weak iv. HClO₃ weak v. NH₄BrO₄ strong vi. C₁₂H₂₂O₁₁ non-electrolyte 4. Tell if a precipitate may form upon mixing each of the following solutions: (You must know the list of solubility rules to answer this question) a. ammonium chloride and lead (II) nitrate.   PbCl₂ (s) b. barium nitrate and potassium sulfate. BaSO₄ (s) c. nickel (II) sulfate and sodium hydroxide. Ni(OH)₂ (s) 5. a. Define: isoelectronic Different species that have the same number and configuration of electrons. b. Which of the following isoelectronic species has the largest size? Se²⁻ Br⁻ Kr Sr²+ # of electrons: 36 36 36 36 # of protons: 34 35 36 38 The smaller the nucleus (charge # of protons), the larger the radius. The shells (energy levels) contract due to the greater attractive force of the nucleus. The radius decreases with increasing atomic number (# of protons). Se²⁻ will have the largest size. 6. Write an equation illustrating a. the heat of formation of of LiCl (s) Le(s) of Licks Cl (g) → Lills) h. the lattice energy of CsBr(s) (s+(g) + Br (g) (s Bris) c. the dissociation energy of Cl2 (g) d. the sublimation energy of Mg (s) Cl₂(g) 2(g) 2 Mg(s) Mg (g) c. the electron affinity of I(g) I (g) + le→ I-(g) g) the first ionization energy of Ca(g) (a (g) (at (g) +ie 7. Consider the types of crystalline solids: a) ionic, b)metallic, c)covalent network, and d) molecular to answer the questions given below: ionic Which conducts electricity in the solid state? metallic Which conducts electricity only in the molten state (liquid state) Which has low melting point? Which is known to be the hardest? molecular cavalent nerwork Which is soft and does not conduct electricity? molecular Which has lattice points occupied by positive and negative ions? Which has lattice points occupied by atoms? Lonic covalent networ 8. List the major intermolecular force in each of the following a) H2 b) NH3 c) OC12 (bent geometry) d) CH.4(tetrahedral geometry) London dipole. dipole hydrogen ercea 9. Kh London Define mota boiling point elevation constant Kr to dissolung i mole of nonvolatile, aben dissociali ng in I fig of If Ks for water is 1.86°C.kg/mole. How many units of degrees will a solution of 1.00 m Mg(C2H302)2 rise in temperature? 3 mots of ions 1-86°C ag I mole compound mole ofirds 10. A large value of an equilibrium constant, like 10"", indicates that the position of equilibrium lies further to the right ES.58°C irigit, of left) 11. Define: Normal boiling point It is the boiling point of a liquid at satm. -2- 12. Draw the phase diagram for water and label the axis and the physical states in each region. 13. State the physical state of the dispersed phase and continuous phase in each of the following colloids: a. a sol: dispersed phase is solid; continuous phase could be solid or liquid. b. an emulsion: dispersed phase is liquid; continuous phase is liquid. c. a gel: dispersed phase is liquid; continuous phase is solid. 14. a. Determine if a decrease in pressure at constant temperature favors the formation of reactants, the formation of products, or neither? 1   i. H₂(g) + Cl₂(g) ⇌ 2HCl(g) - neither ii. 2 KClO₃(s) ⇌ 2 KCl(s) + 3 O₂(g) - products iii. PCl₅(g) ⇌ PCl₃(g) + Cl₂(g) - products b. Which of the above equilibria has Kₚ = Kc? Kp = Kc(RT)^Δn Δn = products - reactants 15. a. What is the equilibrium constant for the reaction given below, if Ka₁ = 1.0 x 10⁻⁷ and Ka₂ = 1.4 x 10⁻¹⁴? H₂S(aq) + 2 H₂O(l) ⇌ 2 H₃O⁺(aq) + S²⁻(aq) Answer: K = (1.0 x 10⁻⁷)²(1.4 x 10⁻¹⁴) = 1.4 x 10⁻²¹ b. What is the [S²⁻] concentration of 0.10 M H₂S(aq)? Answer: [S²⁻] = √K₂ = √(1.4 x 10⁻¹⁴) = 1.4 x 10⁻⁷ 16. Determine if each solution given below is acidic, basic, or neutral at the equivalence point. a. titration of NH₃(aq) by HCl at the equivalence point. NH₄Cl is present. NH₄⁺ will hydrolyze forming acidic solution. b. titration of HCOOH by NaOH at the equivalence point. NaCOOH is present. COO⁻ will hydrolyze forming basic solution. c. titration of NaF and by HCl at the equivalence point. HF is present. No hydrolysis. Solution is neutral. 17. Oxalic acid, H₂C₂O₄, has values of Ka₁ = 5.6 x 10⁻² and Ka₂ = 5.1 x 10⁻⁵. Find Kb for the following equilibrium: HC₂O₄⁻(aq) + H₂O(l) ⇌ H₂C₂O₄(aq) + OH⁻(aq) Answer: Ka₁ * Kb₂ = Kw (5.6 x 10⁻²) * Kb₂ = 1.0 x 10⁻¹⁴ Kb₂ = 1.8 x 10⁻¹³ 18. Determine if each solution given below is a buffer. a. 0.4 mole NH₃ and 0.2 mole HCl Initial NH₃ + HCl → NH₄Cl Change -0.2 -0.2 +0.2 +0.2 Final 0.2 0 0.2 0.2 NH₃ excess and NH₄Cl formed. Buffer. b. 0.5 mole NH₃ and 0.5 mole HCl NH₃ + HCl → NH₄Cl NH₄Cl is produced. Not a buffer. c. 0.2 mole HF and 0.4 mole NaOH HF + NaOH → NaF + H₂O NaF is produced and NaOH is in excess. Not a buffer. d. 0.5 mole HCN and 0.2 mole KOH HCN + KOH → KCN + H₂O HCN excess and KCN is produced. Buffer. 19. Alcohol and water form an ideal solution. At a certain temperature, the vapor pressure of alcohol is 140 torr and that of water is 50 torr. What is the total vapor pressure in a closed container that has a solution made of 2.8 mole alcohol and 7.8 mole water?   Setup: P = Xₐlcohol * P°alcohol + Xwater * P°water = (2.8 mol / (2.8 + 7.8) mol) * 140 torr + (7.8 mol / (2.8 + 7.8) mol) * 50 torr = 37.0 torr + 36.8 torr = 73.8 torr Answer: 73.8 torr 20. A 0.010 M NH₃ solution has [OH⁻] = 1.00 x 10⁻⁵ M. What is the percent dissociation of NH₃ in the solution? Setup: % dissociation = ([OH⁻] / [NH₃]initial) x 100 = (1.00 x 10⁻⁵ mol/L / 0.010 mol/L) x 100 = 0.1% Answer: 0.1% 21. The vapor pressure of water at a certain temperature is 450 torr. What is the vapor pressure of a solution that contains 2.00 moles sugar and 18 moles water at the same temperature?   Setup: P = Xsolvent * P°solvent = (18 moles / (2 + 18) moles) * 450 torr = 405 torr Answer: 405 torr