CHEMISTRY 101Name ______
Hour Exam II
October 30, 2007Signature ______
Adams/Denofrio
Section ______
"When they broke open molecules, they found they were only stuffed with atoms. But when they broke open atoms, they found them stuffed with explosions."
--Science Exam Quote from an 11-Year Old
This exam contains 17 questions on 7 numbered pages. Check now to make sure you have a complete exam. You have one hour and fifteen minutes to complete the exam. Determine the best answer to the first 15 questions and enter these on the special answer sheet. Also, circle your responses in this exam booklet. Show all of your work and provide complete answers to questions 16 and 17.
1-15(30 pts.)______
16 (12 pts.)______
17 (18 pts.)______
Total (60 pts)______
Useful Information:
1.000 L = 1000.0 mL
Always assume ideal behavior for gases (unless explicitly told otherwise).
PV = nRT
R = 0.08206 L·atm/mol·K
K = C + 273
NA = 6.022 x 1023
Solubility Rules:
1. Most nitrate salts are soluble.
2. Most salts of sodium, potassium, and ammonium cations are soluble.
3. Most chloride salts are soluble. Exceptions: silver(I), lead(II), and mercury(I) chloride.
4. Most sulfate salts are soluble. Exceptions: calcium, barium, and lead (II) sulfate.
5. Most hydroxide salts can be considered insoluble. Soluble ones: sodium, potassium, and calcium hydroxide.
6. Consider sulfide, carbonate, and phosphate salts to be insoluble. Soluble ones: sodium and potassium.
CHEMISTRY 101Fall 2007
Hour Exam IIPage No. 1
1.Consider the following unbalanced equation:
After the equation is balanced in standard form, what is the coefficient in front of Na(s)?
a)1b)2c)3d)4e)6
2. Which of the following ions form compounds with Pb2+ that are generally soluble in water?
I.S2–
II.Cl–
III.NO3–
IV.SO42–
V.Na+
a)I, II, IV, and V
b)III and V
c)II, III, and IV
d)III and IV
e)III only
3. How many of the following statements are true about balanced chemical equations?
I.The same numbers of atoms of each element must be present on the reactant side and on the product side.
II.The sum of the coefficients on the reactant side is always equal to the sum of the coefficients on the product side.
III.Only whole numbers can be used to balance a chemical equation.
IV.Subscripts in the formulas can be changed to balance an equation.
a)0b)1c)2d)3e)4
4.Consider the following reaction:
What mass of H2O is needed to completely react with 20.0 g of PCl3?
a)7.87 gb)0.875 gc)5.24 gd)2.62 ge)14.5 g
5. What mass of solid sodium carbonate do you need to prepare 300.0 mL of a 2.00 M sodium carbonate solution?
a) 0.600 gb) 15.9 gc) 49.8 gd) 63.6 ge) 707 g
6. You mix 225.0 mL of a 2.5 M HCl solution with 150.0 mL of a 0.75 M HCl solution. What is the molarity of the final solution?
a) 1.6Mb) 1.8Mc) 3.0Md) 3.3 Me) 4.5 M
7. When referring to the coefficients in a balanced chemical equation, why do we say an individual coefficient is meaningless? Choose the best answer.
a)The coefficients represent how many moles are present in a given sample before and after the chemical reaction takes place.
b)The sum of the coefficients is what’s important. The sum of the coefficients on the reactant side must equal the sum of the coefficients on the product side.
c)It is the ratio of the coefficients between the reactants and products that helps us predict how much product can be made or how much reactant is required.
d)A coefficient is used to multiply what you are given in the problem to determine how much reactant you have.
e)Coefficients? Coefficients are used in balanced chemical equations?
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Use the following scenario to answer questions8 – 9.
Nitrogen and fluorine react to form nitrogen fluoride according to the unbalanced chemical equation
8.For every 4.00 mol of N2 that reacts, ______mol of F2 is required.
a) 0.750 molb) 1.33 molc) 3.00 mold) 4.00 mole) 12.0 mol
9. In which of the following scenarios is N2 the limiting reactant?
I.0.50 mol N2(g) and 0.50 mol F2(g)
II.200 molecules N2(g) and 800 molecules F2(g)
III.1.0 L N2(g) and 2.0 L F2(g) at STP (0°C and 1.00 atm)
a) III only
b) II and III
c) II only
d) I only
e) I, II, and III
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10.A 0.50 M solution of sodium chloride sits on a lab bench. Which of the following would decrease the concentration of the salt solution?
a)Add water to the solution.
b)Pour some of the solution down the sink drain.
c)Add more sodium chloride to the solution.
d)Let the solution sit out in the open air for a couple of days.
e)At least two of the above would decrease the concentration of the salt solution.
11.Consider the equation: . If 1.0 mol of A is reacted with 1.0 mol of B, which of the following statements is true?
a)2.0 mol of C is produced when the reaction is complete.
b)3.0 mol of D is produced when the reaction is complete.
c)The limiting reactant is A because 2/5 mol of A is needed for every 1 mol of B.
d)The reaction begins with 2.0 mol of A and 5.0 mol of B.
e)There is not enough of either reactant A or B for the reaction to proceed.
12.Iron(III) oxide reacts with carbon monoxide to give iron metal and carbon dioxide. If 2.50 mol of carbon dioxide is produced, what mass of iron(III) oxide was required?
a)0.833 gb) 1.25 gc) 1.20 × 103 gd) 249 ge) 133 g
13.Zinc metal reacts with hydrochloric acid to form hydrogen gas via the reaction
How many grams of zinc would be required to produce enough hydrogen gas to fill a 5.00 L container to a pressure of 3.00 atm at 25.0°C? Assume you start with excess HCl.
a) 0.613 gb) 1.24 gc) 40.1 gd) 65.4 ge) 478 g
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Consider the following four solutions to answer questions 14 – 15.
Solution #1:100.0 g of cesium chloride (MM = 168.35 g/mol) dissolved in 1.0 L of water.
Solution #2:100.0 g of sodium sulfate (MM = 142.05 g/mol) dissolved in 1.0 L of water.
Solution #3:100.0 g of cesium fluoride (MM = 151.90 g/mol) dissolved in 1.0 L of water.
Solution #4:100.0 g of sodium phosphate (MM = 163.94 g/mol) dissolved in 1.0 L of water.
14.Which of the solutions above has the highest concentration?
a)Solution #1
b)Solution #2
c)Solution #3
d)Solution #4
e)At least two of the above solutions have the same highest concentration.
15.Which of the solutions above contains the greatest number of ions?
a)Solution #1
b)Solution #2
c)Solution #3
d)Solution #4
e)At least two of the above solutions contain the greatest number of ions.
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16. Consider the following scenario:
You react nitrogen and hydrogen gases in a container to produce ammonia, NH3(g). The following figure depicts the contents of the container after the reaction is complete.
a.Write a balanced chemical equation for the reaction including all phases.
b.What is the limiting reactant? Why? Be thorough in your explanation.
c.How many molecules of hydrogen did you start with before the reaction took place? How many molecules of nitrogen did you start with before the reaction took place?Show all of your work in an organized manner in the space provided.
d.How many molecules of the limiting reactant would you need to add to the container in order to have a complete reaction (convert all reactants to products)? Show all of your work in an organized manner in the space provided.
17.Smarty Student mixes 2.0 L of 0.010 M sodium sulfate and 100.0 mL of 0.20 M calcium chloride in a large, empty beaker.
a.Write the balanced molecular, complete ionic, and net ionic equations below. Include all phases in your reactions.
MOLECULAR:
COMPLETE IONIC:
NET IONIC:
b.What mass of solid (in grams) is produced? Show all of your work in an organized manner in the space provided.
c.What are the concentrations of sulfate ions and sodium ions left in solution after the reaction is complete? Place your final answers in the box below and show all of your work in an organized manner.
d.Smarty’s lab partner (who’s not so smart) accidentally adds 200.0 mL of 0.40 M lead(II) nitrate to the large beaker after the first reaction took place. What is the concentration of lead ions left in solution after the reaction is complete? (HINT: Write the net ionic equation for the reaction that occurs and pay attention to the ions that are left in solution.)Place your final answer in the box below and show all of your work in an organized manner.