Representative Elements Tutorial Problems 2017 students PDF

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Tutorial Problems Group 1A Elements 1. Name each of the following compounds: 2. Write the formulas for each of the following compounds: a. Lithium nitride b. Potassium carbonate

c. Rubidium hydroxide

d. Sodium hydride 3. Complete and balance the following reaction equations. a. Li2O (s) + H2O (l)   b. c. LiH (s) + H2O (l)  

d.

Na2O2 (s) + H2O (l)   KO2 (s) + H2O (l)  

4. Write balanced equation describing the reaction of lithium metal with each of the following: O2, S8, Cl2, P4, H2, H2O and HCl. 5. Lithium reacts with acetylene (HC CH) in liquid ammonia to produce lithium acetylide (LiCCH) and hydrogen gas. Write a balanced equation for this reaction. What type of reaction is this? 6. The electrolysis of aqueous sodium chloride (brine) is an important industrial process for the production of chlorine and sodium hydroxide. Write the balanced equation for the electrolysis of brine (hydrogen gas is also produced).

Group 2A Elements 7. Name each of the following compounds: a. MgCO3 b. BaSO4

c.

8. Write the formula for each of the following compounds: a. Calcium nitrate b. Beryllium chloride

Sr(OH)2

c. Barium hydride

9. The reaction of calcium carbonate with sulfuric acid yields carbon dioxide, water, and calcium sulfate. Write a balanced chemical equation for the reaction of sulfuric acid with calcium carbonate. 10. Write balanced reactions describing the reactions of strontium with each of the following: O 2, S8, Cl2, P4, H2, H2O, and HCl. 11. Predict the structure of BeF2 in the gas phase. What structure would you expect for BeF2 (s)? 12. Draw a Lewis structure for the expected product when BeCl2 reacts with excess ammonia. 13. Slaked lime, Ca(OH)2, is used to soften hard water by removing calcium ions from hard water through the reaction. Ca(OH)2 (aq) + Ca 2+ (aq) + 2HCO3 – (aq) → 2CaCO3 (s) + 2H2O (l) Although CaCO3 (s) is considered insoluble, some of it does dissolve in aqueous solutions. Calculate the molar solubility of CaCO3 in water (Ksp = 8.7 x 10 – 9).

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14. What mass of barium is produced when molten BaC l2 is electrolyzed by a current of 2.50 x 10 5 A for 6.00 h?

Group 3A Elements 15. Write the formula for each of the following compounds. a. Aluminum nitride b. Gallium fluoride

c. Gallium sulfide

16. Thallium and indium form +1 and +3 oxidation states in compounds. Predict the formula of the possible compounds between thallium and oxygen and between indium and chlorine. Name the compounds. 17. Boron hydrides were once evaluated for possible use as rocket fuels. Complete and balance the following equation for the combustion of diborane: 18. Elemental boron is produced by reaction of boron oxide with magnesium to give boron and magnesium oxide. Write a balanced equation for the reaction. 19. Ga2O3 is an amphoteric oxide and In2O3 is a basic oxide. Write equations for the reactions that illustrate these properties. 20. Aluminum hydroxide is amphoteric and dissolves in both acidic and basic solutions. Write balanced chemical equations representing each process. 21. Write equations describing the reactions of Ga with each of the following: F 2, O2, S8, N2, and HCl. 22. Write the balanced equation describing the reaction of aluminum metal with concentrated aqueous sodium hydroxide. 23. Calculate the pH of a 0.050 M Al(NO3)3 solution The Ka value for Al(H2O)6 3+ is 1.4 x 10 – 5.

Group 4A Elements 24. Draw Lewis structures for CF4, GeF4, and GeF62-. Predict the molecular structure (including bond angles), and give the expected hybridization of the central atom in these three substances. Explain why CF62- does not form. 25. Carbon and sulfur form compounds with the formulas CS 2 and C3S2. Draw Lewis structures and predict the shapes of these two compounds. 26. Silicon is produced for the chemical and electronics industries by the following reactions. Give the balanced equation for each reaction. a. SiO2 (s) + C (s)  Si (s) + CO (g) b. Silicon tetrachloride is reacted with very pure magnesium, producing silicon and magnesium chloride. c. Na2SiF6 (s) + Na (s)  Si (s) + NaF (s) 27. Write the equations describing the reactions of Sn with each of the following: C l2, O2, and HCl.

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28. The fermentation of glucose produces methanol and carbon dioxide. Write a balanced reaction for this process. 29. Tin forms compounds in the +2 and +4 oxidation states. Therefore, when tin reacts with fluorine two products are possible. Write balanced equations for the production of two tin halide compounds and name them. 30. Silicon carbide (SiC) is an extremely hard substance. Propose a structure for SiC.

Group 5A Elements 31. Complete and balance each of the following reactions. a. The decomposition of solid ammonium nitrate. b. The composition of gaseous dinitrogen pentoxide c. The reaction between solid potassium phosphide and water. d. The reaction between liquid phosphorus tribromide and water. e. The reaction between aqueous ammonia and aqueous sodium hypochlorite. 32. Write balanced chemical equations describing the reaction arsenic with oxygen and the reaction of the resulting oxide with water. 33. Phosphorus occurs naturally in the form of fluorapatite CaF 23Ca3(PO4)2. This mineral is reacted with an aqueous solution of sulfuric acid in the preparation of a fertilizer. The products are phosphoric acid, hydrogen fluoride, and gypsum, CaSO 42H2O. Write and balance the chemical equation describing this process. 34. Isohypophosphonic acid (H4P2O6) and diphosphonic acid (H4P2O5) are tri- and diprotic acids, respectively. Draw Lewis structures for these acids that are consistent with these facts. 35. One of the most strongly acidic solutions known is a mixture of antimony pentafluoride (SbF5) and fluorosulfonic acid (HSO3F). The dominant equilibria are SbF5 + HSO3F ⇌ F5SbOSO2FH F5SbOSO2FH +HSO3F ⇌ H2SO3F+ + F5SbOSO2FDraw Lewis structures for all the species shown in the preceding reactions. Predict the hybridization of the central Sb and S atoms in each structure. 36. The oxyanion of nitrogen in which it has the highest oxidation state is the nitrate anion (NO 3 – ). The corresponding oxyanion of phosphorus is PO4 3 –. The NO4 3 – ion is known but not stable. The PO3 – ion is not known. Account for these differences in terms of the bonding in the four ions. 37. Air bags are activated when a severe impact causes a steel ball to compress a spring

and electrically ignite a detonator cap. This causes sodium azide (NaN 3) to decompose explosively. What mass of NaN3(s) must be reacted according to 2NaN3(s)  2Na(s) + 3N2 (g) in order to inflate an air bag to 70.0 L (STP)?

Group 6A Elements 38. Complete and balance the following reactions. a. The reaction between sulfur dioxide gas and oxygen gas.

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b. The reaction between sulfur trioxide gas and water. c. The reaction between aqueous sodium thiosulfate and aqueous iodine. d. The reaction between copper metal and aqueous hot sulfuric acid. 39. A sample of powdered sulfur was divided into two parts – one about twice the size of

the other. The smaller sample was heated until the sulfur melted and began to burn. The gaseous product A of this reaction was collected and mixed with water to form B. The larger sulfur sample was mixed with iron filings and heated in a crucible producing a dark solid C. The solid was placed in a container, and HC l was added producing a gas D, which was allowed to mix with A, giving a yellow-to-white finely-divided precipitate E. a. Identify the five substances mentioned above. b. Write chemical equations describing the reactions.

Group 7A Elements 40. Write the Lewis structure for O2F2 (O2F2 exists as F-O-O-F). Assign the oxidation states and formal charges for the atoms in O 2F2. O2F2 is a vigorous and potent oxidizing and fluorinating agent. Are oxidation states or formal charges more useful in accounting for these properties of O2F2? 41. Complete and balance each of the following reactions: a. BaCl2 (aq) + H2SO4 (aq)  b. BrF (s) + H2O (l)  c. SiO2(s) + HF (aq)  42. Hypofluorous acid was obtained using the fluorination of ice. Hypofluorous acid is exceedingly unstable, decomposing spontaneously to HF and O 2. It reacts rapidly with water to produce HF, H2O2, and O2. In dilute acid, H2O2 is the major product; in dilute base, O 2 is the major product. a. Write balanced equations for the reactions described above. b. Assign oxidation states to the elements in hypofluorous acid. Does this suggest why hypofluorous acid is so unstable? 43. Although the ClO4 – and IO4 – ions have known for a long time, BrO4 – ion was not synthesized until 1965. The ion was synthesized by oxidizing the bromate ion with xenon difluoride, producing xenon, hydrofluoric acid and the perbromate ion. Write the balanced equation for this reaction. 44. Commercial bleaching powder is a mixture of Ca(OC l)Cl, CaCl2, and Ca(OCl)2 in approximately equimolar quantities. a. Name these substances.

The powder is prepared by passing chlorine over dry calcium oxide CaO (s) + Cl2 (g)  Ca(OCl)Cl (s) 2CaO (s) + 2Cl2 (g)  Ca(OCl)2 (s) + CaCl2 (s) leaving a small amount of CaO as an impurity. b. Find the oxidation state of chlorine in the compounds given in the equations. c. Identify the oxidizing and the reducing agent in each equation.

The chlorine needed for bleaching is produced in neutral aqueous solution by the reaction between water, OCl - and Cl - represented by the equation OCl - (aq) + Cl- (aq) + H2O (l)  Cl2 (g) + 2OH - (aq)

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d. What element in the above equation is being oxidized and reduced? e. What happens to the pH of the solution as the chlorine is being generated?

Group 8A Elements 45. The xenon halides and oxides are isoelectronic with many other compounds and ions containing halogens. Give a molecule or ion in which iodine is the central atom that is isoelectronic with each of the following. a. Xenon tetroxide b. Xenon trioxide c. Xenon difluoride d. Xenon tetrafluoride e. Xenon hexafluoride 46. For each of the following, write Lewis structure(s), predict the molecular structure (including bond angles), and give the expected hybridization of the central atom. a. KrF2 b. KrF4 c. XeO2F2 d. XeO2F4

Additional Exercises 47. Each of the following compounds is a basic, acidic, or amphoteric oxide:

a. MgO b. P 4O 6 c. Al2O3 For each substance write the equation for the reaction with water, and if possible, with an acid or base. 48. Sodium bismuthate (NaBiO3) is used to test for the presence of Mn 2+ in solution by the following reaction: Mn2+ (aq) + NaBiO3 (s)  MnO4- (aq) + BiO33- (aq) Balance this equation. 49. An unknown element is a nonmetal and has a valence electron configuration ns 2np4. a. How many valence electrons does this element have? b. What are some possible identities for this element? c. What is the formula of the compound this element would form with lithium? d. Would this element have a larger or smaller radius than barium? e. Would this element have a greater or smaller ionization energy than fluorine? 50. Bacterial digestion is an economical method of sewage treatment. The reaction 5CO2 (g) + 55NH4 + (aq) + 76O2 (g)

Bacteria

C5H7O2N (s) + 54NO2 – (aq) + 52H2O (l) + 109H +

→

(aq) Bacterial tissue is an intermediate step in the conversion of the nitrogen in organic compounds into the nitrate ions. How much bacterial tissue is produced in treatment plant for every 1.0 x 10 4 kg of wastewater containing 3.0% NH4 + ions by mass? Assume that 95% of the ammonium ions are consumed by the bacteria.

51. Indium (III) phosphide is a semiconducting material that has been frequently used in lasers, light-emitting diodes (LED) and fiber-optics devices. This material can be synthesized at 900. K according to the following reaction: In(CH3)3 (g) + PH3 (g) → InP (s) + 3CH4 (g) a. If 2.56 L of In(CH3)3 at 2.00 atm is allowed to react with 1.38 L of PH 3 at 3.00 atm, what mass of InP (s) will be produced assuming the reaction is 87% efficient?

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b. When an electric current is passed through an optoelectronic device containing InP, the light emitted has an energy of 2.0 x 10 – 19 J. What is the wavelength of this light and is it visible to the human eye? c. The semiconducting properties of InP can be altered by doping. If a small number of phosphorus atoms are replaced by atoms with an electron configuration of [Kr]5s 24d105p4, is this n-type or p-type doping? 52. The compound NF3 is quite stable, but NCl3 is very unstable (NCl3 was first synthesized in 1811 by P. L. Dulong, who lost three fingers and an eye studying its properties). The compounds NBr3 and NI3 are rare, although the explosive compound NI 3·NH3 is known. Account for the instability of these halides of nitrogen. 53. The structure of TeF5- is

-

F 79

o

F

F Te

F

F

Draw a complete Lewis structure for TeF5-, and explain the distortion from the ideal square pyramidal structure. 54. Predict the molecular structure for each of the following:

a. BrFI2 b. XeO2F2 c. TeF2Cl3For each formula there are at least two different structures that can be drawn using the same central atom. Draw all possible structures for each formula. 55. Describe the bonding in the O3 molecule, the NO2-, and the CO32- ion, using the localized electron bond model. How would the molecular orbital model describe the  bonding in these two species? 56. You travel to a distant, cold planet where ammonia flows like water. In fact, the inhabitants of this planet use ammonia (an abundant liquid in their planet) much as earthlings use water. Ammonia is also similar to water in that it is amphoteric and undergoes autoionization. The K value for the autoionization is 1.8 x 10 – 12 at the standard temperature of the planet. What is the pH of ammonia at this temperature? 57. Although nitrogen trifluoride (NF3) is a thermally stable compound, nitrogen triiodide (NI 3) is known to be a highly explosive compound. NI3 can be synthesized according to the equation: BN (s) + 3IF (g) → BF3 (g) + NI3 (g) a. What is the enthalpy of formation of NI 3 (s) is given the enthalpy of reaction (– 307 kJ) and the enthalpies of formation for BN (s) (– 254 kJ/mol), IF (g) (– 96 kJ/mol), and BF 3 (g) (– 1136 kJ/mol)? b. It is reported that when the synthesis of NI 3 is conducted using 4 mol IF for every mol BN, one of the by-products isolated is [IF2]+[BF4]–. What are the molecular geometries of the species in this by-product and what are the hybridizations of the central atoms in each species?

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58. Magnetite (Fe3O4) contains a mixture of Fe ratio of Fe 2+ and Fe 3+ in Fe3O4?

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2+

and Fe

3+

oxidation states. What is the mole...