Advanced Placement
Chemistry
Midterm Exam
January 30th, 2014 9:00am
Name: _______________________________________
Section
Description
Pts
A
Multiple Choice
75
B
Constructed Response
50
C
Experimental
25
Score
/150
%
This practice exam is much longer than the actual exam. It has been created to give an idea
of question types, question difficulty, and topic spread. Complete this with your books
closed and correct from responses on the website
Part A: Multiple Choice
Part B: Constructed Response
1.
Chlorine dioxide gas (ClO2) is used as a commercial bleaching agent. It bleaches materials by oxidizing
them. In the course of these reactions the ClO2 is itself reduced.
(a) What is the Lewis structure for ClO2? [2 pt]
(b) Suggest a reason as to why ClO2 is reduced so readily ? [3 pts]
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(c) When ClO2 molecule gains an electron chlorite forms, ClO2-1. Draw the Lewis structure of this ion.
[2 pts]
(d) Predict the O-Cl-O bond angle in the ClO2-1 ion. [2pts]
1.
(e) One method for preparing chlorine dioxide is by reacting chlorite with sodium chlorite
__Cl2(g) + __NaClO2(s) →__ClO2(g)+ __NaCl(s)
If you allow 10.0g of NaClO2 to react with 2.00L of Cl2(g) at a pressure of 1.50atm at 21°C, how many
grams of ClO2 can be prepared? [4 pts]
2.
Explain Rutherford’s gold foil experiment: cover briefly its implications, how it it was conducted, and
why it changed how we thought of the atom? [4 pt]
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3.
A sample of 5.53g of Mg(OH)2 is added to 25.0ml of 0.200M HNO3(aq)
(a) Write the chemical equation for the reaction that occurs. [2 pts]
(b) What is the limiting reactant in this reaction? Show your work. [3 pts]
(c) How many moles of Mg(OH)2, HNO3, and Mg(NO3)2 are present after the reaction is complete?
[3 pts]
4.
Calculate the formal charge on the indicated atom in each of the following molecules of ions: [6 pts]
(a) the central atom on O3
(b) phosphorus in PF6-1
(c) nitrogen in NO2
5.
Federal regulations set an upper limit of 50 parts per million (ppm) of NH3 in the air in a work
environment (that is, 50 molecules of NH3(g) for every million molecules in the air). Air from a
manufacturing operation was drawn through a solution containing 1.00 x 10 2ml of 0.0105M HCl. The
NH3 reacts with HCl as follows:
NH3(aq) + HCl(aq) → NH4Cl(aq)
After drawing air through the acid solution for 10.0min at a rate of 10.0L/min, the acid was titrated.
The remaining acid needed 13.1ml of 0.0588M NaOH to reach the equivalence point.
(a) How many grams of NH3 were drawn into the acid solution? [3 pts]
(b) How many ppm of NH3 were in the air? (Air has a density of 1.20g/L and an average molar mass of
29.0g/mol under the conditions of the experiement.) [4 pts]
(c) Is this manufacturer in compliance with regulations? [1 pt]
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6.
Complete combustion of 1 mol of acetone (C3H6O) liberates 1790kJ:
(a) Write the combustion equation for the above process: [3 pts]
(b) Using the Appendix C data booklet determine the enthalpy of formation of acetone. [4 pts]
7.
Write balanced equations for the following reactions: [4 pts]
(a) Potassium oxide with water
(b) diphosphorus trioxide with water
(c) chromium (III) oxide with dilute hydrochloric acid
(d) selenium dioxide with aqueous potassium hydroxide
Part C: Experimental
A teacher assigns his students to make A.S.A. using salicylic acid and acetic anhydride in excess. If 3.00g of
salicylic was used:
(a) Write the equation showing the above reaction [3 pts]
(b) If 2.85g of product is obtained, what is the percent yield? [5 pts]
(c) After the product is dried your teacher asks for you to determine the purity of your product. 500.0mg of
the product is dissolved in ethanol and an indicator is added to the flask. You have standardized NaOH of
0.150M.
(i) If 3 trials are completed producing 12.4ml, 12.8ml, and 12.5ml of NaOH used each time.
Report the average mg of ASA from the sample and confidence limit ( t = 4.303) [9 pts]
1.
(ii)
Determine the % composition of ASA in your product for each trial. Average and show a confidence
limit at the 95% C.L. (t = 4.303) [6 pts]
2.
Suggest any errors that could happen during this experiment [2 pt]
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