AP FINAL EXAM REVIEW #3 1) Draw 2 resonance structure for each of the following chemical formulas. Also, give the formal charge for each atom in the structure and determine which structure will be most stable. a) SO42-
b) CO32-
c) PO43-
2. Beaker X and beaker Y each contain 1.0 L of solution, as shown above. A student combines the solutions by pouring them into a larger, previously empty beaker Z and observes the formation of a white precipitate. Assume that the volumes are additive. a) Which ion has the greatest concentration? Explain. b) Did both solution have the same molarity? Explain c) If the molarity of the AgNO3 solution was 1.0M, what was the molarity of the MgCl2 solution? d) What is the molarity of the Mg(NO3)2 in the Beaker Z. 3. A CPHS student performs a reaction using 3.5g iron metal and 10.00g of CuSO 4. The chemical reactions is as follows. Fe(s) CuSO4(aq) → Cu(s) FeSO4(aq) a)
Which substance is the limiting reagent? Explain your answer.
b)
Before proceeding with experiment the student needs to make a 0.500M solution
c)
Calculate the theoretical yield of iron sulfate for this reaction.
d)
Provide the oxidation and reduction half reactions for this experiment. Clearly indicate which reaction is oxidation and which is reduction. Also, indicate the oxidizing agent and the reducing agent.
4. Propane is a hydrocarbon that is commonly used as a fuel for cooking. Propane’s formula is C3H8. a) Balance the equation for the complete combustion of propane gas. __C3H8 + __O2 → __ CO2 + __ H2O b) Calculate the volume of air at 0°C and 1.00 atm that is needed to burn completely 20.0 g of propane. Assume that air is 21.0% O2 by volume. c) The heat of combustion (ΔH°combustion) is -2,220.1 kJ/mol. Calculate the heat of formation, ΔH°f, of propane given that ΔHf of H2O(l) is -285.3 kJ/mol and ΔH°f of CO2(g) is -393.5 kJ/mol.
Mass of KI tablet
0.425 g
Mass of thoroughly dried filter paper
1.462 g
Mass of filter paper + precipitate after first drying
1.775 g
Mass of filter paper + precipitate after second drying
1.699 g
Mass of filter paper + precipitate after third drying
1.698
5. A student is given the task of determining the I− content of tablets that contain KI and an inert, water-soluble sugar as a filler. A tablet is dissolved in 50.0 mL of distilled water, and an excess of 0.20 M Pb(NO3)2(aq) is added to the solution. A yellow precipitate forms, which is then filtered, washed, and dried. The data from the experiment are shown in the table above. (a) For the chemical reaction that occurs when the precipitate forms, (i) write a balanced, net-ionic equation for the reaction, and (ii) explain why the reaction is best represented by a net-ionic equation. (b) In the filtrate solution, is [K+] greater than, less than, or equal to [NO3−] ? Justify your
answer. (c) Calculate the number of moles of precipitate that is produced in the experiment. (d) Calculate the mass percent of I− in the tablet. (e) In another trial, the student dissolves a tablet in 55.0 mL of water instead of 50.0 mL of
water. Predict whether the experimentally determined mass percent of I − will be greater than, less than, or equal to the amount calculated in part (e). Justify your answer.
6. Answer the following questions related to the reaction and information provided:: C2H4(g) + F2(g) → C2H4F2(g) a) Find the heat of reaction.
Bond C-C C-H C=C F-F C-F
Bond energy (kj/mol) 347 413 614 154 485
b) How does the distance between the two carbon atoms change as you go from reactant to product. Explain. c) Provide the hybridization and geometry for the carbons in the reactant and the product.
