The following practice examination contains 32 questions. Thursday s examination will contain 32 questions valued at 3.

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1 Chemistry 121 Exam 2 Practice Spring 2018 The following practice examination contains 32 questions. Thursday s examination will contain 32 questions valued at 3.5 points/question Name KEY 1. Which of the following contains no ionic bonds? a. KCl (s) b. NaCl (s) c. LiCl (s) d. Cl (g) e. All contain an ionic bond ydrogen and chlorine are non-metals. The key is the subscript (g) hydrochloric acid, Cl (aq) is very much ionic as Cl is a strong acid, by definition completely donating + to water when the 2 are mixed, generating 3O + and Cl - 2. What is the formula of the compound that forms when elemental lithium reacts with elemental oxygen? Li 2 O It s all about the noble gas electronic configuration 3. What is the charge on the phosphate ion? a. +3 b. +1 c. 0 d. -1 e. -3 Nick the Camel ate a Clam Supper in Phoenix. Phosphate is -3 (3 vowels in Phoenix)

2 4. What is the charge on trihydrogen phosphate? a. +3 b. +1 c. 0 d. -1 e. -3 A bit tricky perhaps but trihydrogen phosphate = phosphoric acid with no charge. Every time you put an ( + really) on phosphate you lose a negative charge. Every time you pull an ( + really) off of phosphoric acid you gain a negative charge 5. What is the charge on oxygen when it forms 3 covalent bonds? a. +2 b. +1 c. 0 d. -1 e. -2 Oxygen shares its 2 single electrons to form 2 covalent bonds. If it uses one of its non-bonded pairs of electrons to form a coordinate covalent bond, it becomes positive (think of 3O + being generated when an acid is dissolved in water) Please name the following compounds 6. CaF2 Calcium fluoride 7. N4O Ammonium hydroxide 8. Cr(NO3)3 Chromium(III) nitrate 9. Ag2S Silver(I) sulfide 10. CO2 Carbon dioxide

3 Please provide the formula for the following compounds 11. Potassium iodide KI 12. Sodium hydrogen sulfate NaSO4 13. Ammonium sulfide (N4)2S 14. Cadmium(II) sulfide CdS Cadmium salts constitute pigments in the yellow, orange, and red range. CdS is cadmium yellow. It is surprising they are used as extensively as they are given Cd is toxic (one of 6 banned substances by the EU s Restrictions on azardous Substances Directive). Also used extensively in Ni-Cd battery production. 15. Dihydrogen dioxide 2O2 Bonus: On questions drawing one additional isomer with earn you 1.75 extra credit points 16. Draw an acceptable Lewis structure for C48O2. Show appropriate geometry and include non-bonded pairs of electrons if applicable. Don t forget to include non-bonded pairs of electrons and show reasonable geometries. Many other isomeric possibilities exist 17. Draw an acceptable Lewis structure for C23N. Show appropriate geometry and include non-bonded pairs of electrons if applicable. C C N C C N Don t forget to include non-bonded pairs of electrons and show reasonable geometries. A few other isomeric possibilities exist.

4 18. Draw an acceptable Lewis structure for C22O2. Show appropriate geometry and include non-bonded pairs of electrons if applicable. Don t forget to include non-bonded pairs of electrons and show reasonable geometries. Not many other stable isomeric possibilities exist. 19. Which of the following molecules is the most polar? a. O2 (g) b. 2 (g) c. Cl2 (g) d. Cl (g) e. 2 O (g) (a) through (c) are completely non-polar. Oxygen is more electronegative than chlorine. Yes, water exists principally in the liquid phase under standard conditions, but a small amount is ordinarily found in the gas phase (we will talk about relative humidity later in the quarter) 20. Which of the following molecules would dissolve best in water? a. C3C2C2C2O b. C3C2C2C2Cl c. C3C2C2C2S d. OC 2 C 2 C 2 O e. All dissolve equally well Best ratio of highly electronegative oxygen to carbon completely soluble at 2:3 or 1: Which of the following molecules would dissolve best in a non-polar solvent like octanol (C818O)? a. C3C2C2C2O b. C3C2C2C2Cl c. C 3 C 2 C 2 C 2 S d. OC2C2C2O e. All dissolve equally well Electronegativity values O > Cl > S C >. Like dissolves like. The electronegativity table in your book is very good.

5 22. Please balance the reaction for the combustion of glucose 1C612O6 + 6O2 6CO2 + 62O The evils of sugar 23. Please balance the following acid-base reaction. 13PO4 + 3KO 1K3PO4 + 32O 24. Please balance the following acid-base reaction. 13PO4 + 1Ba(O)2 1BaPO4 + 22O Not enough hydroxide to pull off all 3 hydrogens. Note the 2 hydroxide give 2 water molecules 25. What is the formula weight (molar mass) of sodium bicarbonate (sodium hydrogen carbonate)? a g/mol b g/mol c g/mol d g/mol e g/mol NaCO 3: (23.0 x 1) + (1.0 x 1) + (12.0 x 1) + (16.0 x 3) = 84.0 g/mol. Best make certain you have those nomenclature rules down 26. ow many mol are equivalent to 42 g of sodium bicarbonate? a mol b mol c mol d. 1.0 mol e. 1.6 mol 42 g(mol/84.0 g)

6 27. Write the net ionic equation when solutions of K3PO4 and KNO3 are mixed. If there is no reaction, write N.R. Only cation available is K + N.R. 28. Write the net ionic equation when solutions of CuCl2 and K2SO4 are mixed. If there is no reaction, write N.R. Possibilities are CuSO4 and KCl N.R. 29. Write the net ionic equation when solutions of (N4)2CO3 and CaCl2 are mixed. If there is no reaction, write N.R. Possibilities are (N4)Cl and CaCO3 Ca +2 (aq) + CO3-2 (aq) CaCO3 (s) Working backwards from the formula of the precipitate helps in writing the net ionic equation 30. Write the net ionic equation when solutions of KO and MnBr2 are mixed. If there is no reaction, write N.R. Possibilities are Mn(O)2 and KBr Mn +2 (aq) + 2O -1 (aq) Mn(O)2 (s) Use the 2 Br - to determine the charge on manganese

7 31. Please give the products of the following balanced acid-base reaction. If there is no reaction, write N.R. 3PO4 + 3NaO Na3PO4 + 32O See question 23. ydroxide is a strong base (think angry water that has had an + jacked and it wants it back). Phosphoric acid is just that an acid, willing to give up +. Which ones are the acids the polyatomic ions gives you a very good idea, since they are what is left behind when the acid form has lost its hydrogens 32. Please give the products of the following balanced acid-base reaction. If there is no reaction, write N.R. 3PO4 + 2SO4 NR Acids don t react with acids, bases don t react with bases