7. Relax and do well.

Transcription

1 CHEM 1014 Exam III John III. Gelder November 18, 1999 Name TA's Name Lab Section INSTRUCTIONS: 1. This examination consists of a total of 7 different pages. The last page includes a periodic table and some useful information. All work should be done in this booklet. 2. PRINT your name, TA's name and your lab section number now in the space at the top of this sheet. DO NOT SEPARATE THESE PAGES. 3. Answer all questions that you can and whenever called for show your work clearly. Your method of solving problems should pattern the approach used in lecture/discussion. You do not have to show your work for the multiple choice (if any) or short answer questions. 4. Point values are shown next to the problem number. 5. Budget your time for each of the questions. Some problems may have a low point value yet be very challenging. If you do not recognize the solution to a question quickly, skip it, and return to the question after completing the easier problems. 6. Look through the exam before beginning; plan your work; then begin. 7. Relax and do well. Page 2 Page 3 Page 4 Page 5 Page 6 TOTAL SCORES (29) (20) (25) (16) (10) (100)

2 CHEM 1014 EXAM III PAGE 2 (5) 1. Complete the following table Substance # valence electrons K 1 S 6 Ag 1 N 3 8 Na + 8 (10) 2. Predict the formula of the compound formed between the following pairs of elements. a) Mg and O 2 MgO b) Al and sulfur Al 2 S 3 c) potassium and bicarbonate KHCO 3 d) barium and sulfate BaSO 4 e) C and Cl 2 CCl 4 (14) 3. Complete the following table; Name of the compound Formula of the compound Sodium nitrite NaNO 3 Barium hydroxide Ba(OH) 2 ammonia NH 3 Lithium iodide LiI Zinc phosphate Zn 3 (PO 4 ) 2 Sodium carbonate Na 2 CO 3 Magnesium sulfate MgSO 4

3 CHEM 1014 EXAM III PAGE 3 (20) 4. Answer each of the following a) Provide a brief description of what is meant by the term cation. A cation is an ion with a positive charge, it has fewer electrons than protons. b) Provide a brief description of what is meant by the term anion. An anion is an ion with a negative charge, it has more electrons than protons. c) What kinds of compounds contain cations and anions? Ionic compounds d) What is the name of the bond between cation(s) and anion(s)? Ionic bonds e) What is the nature of the bond (attraction) in these compounds? (That is, what holds the ions together to make the bond?) Electrostatic attractions attractions due to the opposite charges on the ions. f) An ion that we have not discussed in great detail is NH 4 +. Draw a Lewis structure of this polyatomic ion. g) Write a formula for the compound of this ion combined with each of the ions Cl -, CO 3 2-, PO NH 4 Cl (NH 4 ) 2 CO 3 (NH 4 ) 3 PO 4 h) NH 4 + is called the ammonium ion. Provide the name for each compound in g). NH 4 Cl ammonium chloride (NH 4 ) 2 CO 3 ammonium carbonate (NH 4 ) 3 PO 4 ammonium phosphate

4 CHEM 1014 EXAM III PAGE 4 (15) 5. Draw the Lewis structure for each of the following compounds/elements. (Show all bonding and nonbonding electrons.) a) CHCl 3 b) OF 2 c) N 2 d) ONCl e) N 2 H 4 (10) 6. What is the molecular geometry/shape of the following compounds. (Note: In the case of N 2 H 4 provide the molecular geometry around each nitrogen.) Substance H 2 S OF 2 CHCl 3 N 2 H 4 H 2 CO Molecular geometry/shape bent bent tetrahedral pyramidal (Trigonal) planar

5 CHEM 1014 EXAM III PAGE 5 (12) 7. Draw and name six structural isomers for the compound C 7 H 16. (Be sure to clearly show all bonds between carbon and hydrogen.) n-heptane 2-methylhexane 3-methylhexane 3,3-dimethylpentane 2,2-dimethylpentane

6 CHEM 1014 EXAM III PAGE 6 2,3-dimethylpentane (4) 8. Are there any structural isomers of the compound C 10 H 22 with a parent chain five carbons long? If so draw an example and name the compound. If there are no structural isomers with a parent chain of five carbons, briefly explain why. 2,2,3,3,4-pentamethylpentane or 2-methyl-3,3-diethylpentane

7 CHEM 1014 EXAM III PAGE 7 (6) 9. Name or draw the Lewis structure for the following organic compounds 3-methyl-4,4-diethylheptane 2,3,4-trimethylhexane 2,5-dimethylheptane (4) 10. The equation for the formation of magnesium chloride is, Mg(s) + Cl 2 (g) --> MgCl 2 (s) We see the formula Cl 2 appears on both sides of the equation. Using a diagram(s) or words explain the difference in the bonding in the two substances containing chlorine. In the reactants chlorine is in the elemental form with a covalent bond between the two chlorine atoms. In the product MgCl 2 is an ionic compound. Although Cl 2 is in the formula since the compound is ionic MgCl 2 contains ions Mg 2+ ion and 2 Cl - ions, there are no Cl 2 molecules.

8 CHEM 1014 EXAM III PAGE IA 1 H Li IIA 4 Be Na Mg K Ca Rb Sr Cs Ba Fr (223) Ra IIIA IVA VA VIA VIIA B C N O F 9 10 Ne IIIB IVB VB VIB VIIB VIII IB IIB Sc Ti V Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br Kr Y Zr Nb Mo Tc Ru Rh Pd Ag Cd In Sn Sb Te I Xe (98) La Periodic Table of the Elements Hf Al Si P S Cl VIIIA 2 Ta W Re 75 Os Ir Pt Au Hg 80 Tl Pb Bi Po At Rn (209) (210) Ac Rf Db Sg Bh Hs Mt (261) (262) (263) (262) (265) (266) He Ar (222) Lanthanides Actinides Ce Pr Nd Pm Sm Eu Gd Tb Dy Ho Er Tm Yb Lu (145) Th Pa U Np Pu AmCm Bk Cf Es Fm Md No Lr (244) (243) (247) (247) (251) (252) (257) (258) (259) (260) Useful Information