CHM 115 EXAM #3 Practice

Transcription

1 Name CHM 115 EXAM #3 Practice Complete the following showing all of your work. When calculations are required, show the set-up, units, and report answers with the correct number of significant figures. Short answers should be composed of well-organized thoughts and written in full sentences. (20 points for completion of BOTH parts (a) and (b)) 1. (a) In the spaces provided, do the following for BrF 5 Draw the BEST Lewis structure of this interhalogen molecule and show formal charge calculations for each type of atom Give the names of (a) the electron pair geometry and (b) the molecular shape, (a) (b) Specify the hybridization of the Br AND draw the energy diagram for the hybridized orbitals (you know - the boxes with electrons in them). Is this species polar or nonpolar? Explain. (b) In the spaces provided, do the following BrF 3 Draw the BEST Lewis structure of this interhalogne molecule and show formal charge calculations for each type of atom Give the names of (a) the electron pair geometry and (b) the molecular shape, (a) (b) Specify the hybridization of the Br AND draw the energy diagram for the hybridized orbitals (you know - the boxes with electrons in them). Is this species polar or nonpolar? Explain.

2 (20 points) 2. For the following two species complete the tasks specified below in a - d. i. CH3COOH ii. C 2 H 2 a. Draw the best Lewis structures. b. Specify the hybridization of both the C atoms and the O atom specified in (i) and the C atoms in (ii)? 3 c. Show the energy level diagram for both the C atoms and the O atom in (i) and the C atoms in (ii), fill the diagrams with the correct number of valence electrons, and identify the types of electrons present (i.e. σ, π, lone pair) 3 d. What are the bond angles around both the C atoms and the O atom in (i) and the C atoms in (ii)? 3 (10 points) 3. Reaction of solid white phosphorus (P 4 ) with chlorine gas (Cl 2 ) yields phosphorus trichloride as the sole product at 100 % yield. (a) Write a balanced chemical equation. (b) When 1.00 g of solid white phosphorus (P 4 ) is reacted with excess chlorine gas (Cl 2 ), determine the maximum amount of PCl 3 that can be formed? 2

3 4. (20 points) Fill in the MO energy diagrams for the species listed below. The answer the questions that appear under the MO energy diagram of each species. nitrogen Ν 2 pernitride Ν 2 2 σ 2p σ 2p π 2p π 2p π 2p π 2p π2p π2p π2p π2p σ2p σ 2s σ2s σ*1s σ1s σ2p σ 2s σ2s σ*1s σ1s Show the calculation of the bond order for nitrogen. Show the calculation of the bond order for the above ion. Is nitrogen diamagnetic or paramagnetic? Explain your answer. Is the above ion diamagnetic or paramagnetic? Explain your answer. Draw the Lewis structure of nitrogen. Draw the Lewis structure for the above ion. Does the bond order for nitrogen from the Lewis structure match the bond order from the MO diagram? Does the bond order for the above ion from the Lewis structure match the bond order from the MO diagram? Which should have the longer, weaker bond; nitrogen or the above ion? Explain your choice! 3

4 (12 points) 5. C4H10 (g) + O2 (g) à CO2 (g) + H2O (l) a. Balance the reaction above. b. If 25.0 g of C4H10 reacts with g of O2, how much CO2 (in BOTH moles and grams) can be formed? Show which reactant is the limiting reactant!! c. If the dry CO 2 is collected and has a mass of 74.6 g, what is the % yield? (8 points) 6. Balance the following redox reaction in acidic solution. I - - (aq) + MnO 4 (aq) I 2 (aq) + Mn 2+ (aq) (7 points) 7. A 5.00 ml sample of battery acid [H 2 SO 4 (aq)] is completely neutralized (converted to aqueous sodium sulfate and water) by ml of M sodium hydroxide [NaOH (aq)]. Complete and balance the reaction and calculate the molarity of the original 5.00 ml H 2 SO 4 (aq) sample. By calculation, demonstrate that the acid in the optimal concentration range (between M) H 2 SO 4 (aq) + NaOH (aq) 4

5 BONUS: for up to 6 points (total) Write the products for the reactions listed below and make sure the reactions are balanced molecular (that is total) equations. Also, name the type of reaction (oxidation-reduction, acid-base neutralization, or precipitation) in the blank to the right. (2 points each) a. Ba (s) + O 2 (g) b. HCl (aq) + Ba(OH) 2 (aq) c. AlCl 3 (aq) + AgNO 3 (aq) 5