Chem 20 Review Questions

Modified True/FalseIndicate whether the statement is true or false. If false, change the identified word or phrase to make the statement true.

____ 1. Ammonia, NH3(l), and PH3(l) have the same molecular shape but different boiling points because ammonia is a polar molecule. ____________________

____ 2. Ionic solids generally have lower melting and boiling points compared to molecular solids. ____________________

____ 3. Intermolecular bonding refers to bonding forces that act between molecules when substances are in the liquid or solid state. ____________________

____ 4. When drawing the Lewis structure of carbon dioxide, the carbon atom shares four valence electron pairs with each oxygen atom in the molecule. ____________________

____ 5. According to Avogadro’s law of combining volumes, gases contain different numbers of molecules at different temperatures and pressures. ____________________

____ 6. Hydrogen bubbles are the cause of a diving danger called “the bends,” which occurs when divers ascend too quickly to the surface. ____________________

____ 7. Breaking existing bonds releases energy. ____________________

____ 8. The balance that exists when a solute both dissolves and crystallizes at the same rate is known as chemical equilibrium. ____________________

____ 9. Neutralization reactions are reactions that involve hydronium ions and hydrogen ions. ____________________

____ 10. The hydronium ion concentration of a solution with a pH of 4.40 is 4.0 10–5 mol/L. ____________________

____ 11. Acid-base indicators are substances that change state when the pH of a solution changes. ____________________

____ 12. When sodium cyanide dissociates, the entity that can change the pH is sodium ion. ____________________

____ 13. 1.00 mol/L hydrofluoric acid has a higher pH than 1.00 mol/L hydrochloric acid. ____________________

____ 14. The ions that do not change during a reaction are called spectator ions. ____________________

____ 15. The percent yield is the actual yield of a product expressed as a percentage of the calculated theoretical yield of that product. ____________________

____ 16. To determine if a limiting reactant is completely used up, the method of titration completeness is often used. ____________________

____ 17. The solution that is transferred from the burette into the flask is called the sample. ____________________

____ 18. The point at which the exact theoretical amount has been added to completely react with the sample is called the equivalence point. ____________________

____ 19. When bromothymol blue changes from its acid form to its base form, the colour of the solution changes from blue to yellow. ____________________

Multiple ChoiceIdentify the choice that best completes the statement or answers the question.

____ 1. According to the Lewis model of the atom, the number of bonding electrons in a nitrogen atom isA. 1B. 2C. 3D. 5

____ 2. Hydrogen fluoride and water have many similar intermolecular bonds, which account for their high melting and boiling points. The intermolecular bonds that they both possess areA. London forces onlyB. London forces and dipole-dipole forces onlyC. Hydrogen bonding onlyD. London forces, dipole-dipole forces, and hydrogen bonding

____ 3. The molecular shapes for carbon tetrachloride and hydrogen bromide areA. linear and angularB. tetrahedral and V-shapedC. tetrahedral and linearD. pyramidal and linear

Table 3.2 Molecular Compounds and their ShapesMolecular compound Shape

I H2S(g) angular (V-shaped)II PH3(g) trigonal pyramidalIII C2H6(g) tetrahedralIV C2H4(g) trigonal planar

____ 4. Use Table 3.2 to answer the following question.

The substance with the same molecular shape as phosphorus trihydride, PH3(g), isA. H2OB. NH3

C. N2H4

D. P2O5

____ 5. The compound with both ionic and covalent bonds isA. ammonium carbonateB. iron(III) oxideC. diphosphorus pentoxideD. hydrogen peroxide

____ 6. A central atom with four bonding electrons is found in which molecular compound?A. NH3(g), ammoniaB. H2O(g), water vapourC. CH4(g), methane gasD. C2H4(g), ethylene gas

____ 7. Pure oxygen boils at –183 C and freezes at –219 C. What state will the oxygen be in if the temperature is brought to within 50 K of absolute zero?A. solidB. liquidC. gasD. plasma

____ 8. Which of the following is a gas-in-liquid type of solution?A. water in airB. carbon dioxide in waterC. methanol in waterD. vinegar

____ 9. Which of the following contains 1 mol of dissolved copper(II) nitrate?A. 500 mL of a 0.5 mol/L solutionB. 750 mL of a 0.75 mol/L solutionC. 500 mL of a 2.0 mol/L solutionD. 1 L of a 0.9 mol/L solution

____ 10. Which of the following cations in solution would precipitate the ion?A. Na+

B. Ca2+

C. Fe3+

D. none of the above

____ 11. Which of the following is not a strong acid?A. hydrochloric acidB. hydrofluoric acidC. sulfuric acidD. nitric acid

____ 12. How much more acidic is vinegar (pH = 2.0) than coffee (pH = 5.0)?A. 3.0B. 1000C. 100D. 2.5

____ 13. Which of the following is not a property of bases?A. They react with active metals.B. They taste bitter and feel slippery.C. They have a pH greater than 7.D. They turn red litmus blue.

____ 14. During an investigation, a technician tested three samples of the same solution with three indicators. The results are shown in the following table.Indicator Colourbromothymol blue yellowbromocresol green bluelitmus red

The technician determined that the pH of the sample is:A. lower than 3.8B. between 3.8 and 5.4C. between 7.6 and 8.0D. between 5.4 and 6.0

____ 15. Which of the following is a polyprotic acid?A.B.C.D.

____ 16. The combustion of any hydrocarbon always yields carbon dioxide and water. Determine the coefficient of the hydrocarbon when the following equation is correctly balanced:

A. 8B. 5C. 6D. 1

Scenario 8.1 Titration Analysis 1

A group of students performed a titration analysis. The results are given in the graph below.

____ 17. Use Scenario 8.1 to answer the following question.

The volume of titrant added at the equivalence point isA. 0.0 mLB. 5.0 mLC. 10.0 mLD. 15.0 mL

Scenario 8.3 Titration Analysis 3A lab group decides to test a manufacturer’s claim that an antacid product contains 200 mg of sodium bicarbonate. Each tablet was placed into an Erlenmeyer flask, 10.00 mL of water was added, and then the tablets were crushed. An indicator was added to each flask, and then each sample was titrated with 0.200 mol/L hydrochloric acid. The titration evidence was collected in Table 8.3.

Table 8.3 Titration of 10.00 mL of NaHCO3(aq) with 0.200 mol/L HCl(aq)Trial 1 2 3 4Final burette reading (mL) 11.6 21.7 31.7 41.8

Initial burette reading (mL) 0.6 11.6 21.7 31.7

Volume of HCl(aq) added (mL)

Indicator colour red orange orange orange

____ 18. Use Scenario 8.3 to answer the following question.

The calculated mass of sodium bicarbonate in the antacid tablet is:A. 169 mgB. 173 mgC. 84.6 mgD. 86.5 mg

CompletionComplete each statement.

1. Electron transfers result from the large difference in ____________________ between metals and nonmetals.

2. A bond that is somewhere between an ionic bond and a covalent bond is called a ______________________________ bond.

3. If the pressure of a gas is reduced by half and the temperature is doubled, the new volume of the gas will be ____________________ times ____________________.

4. As the temperature of a solution decreases, the ____________________ of most solid solutes decreases.

5. The increasing concentration of a harmful pollutant in the ecosystem is called ____________________.

6. The goal of science is to understand and explain the ____________________ world.

7. ____________________ is a common technique for separating a solid product from a liquid. This technique is used in experimental designs for testing stoichiometric predictions.

Matching

Match each item with the correct description below.A. O3 F. ArB. CO2 G. CH4

C. He H. COD. O2 I. Cl2

E. N2 J. SO3

____ 1. a greenish gas used as a weapon during the First World War and now used in water treatment plants

Match the following terms with their descriptions below.A. kinetic molecular model E. Charles’ lawB. real gas F. Gay-Lussac’s lawC. density of a gas G. ideal gasD. molar volume at SATP H. 22.4 L

____ 2. the volume of one mole of gas at 0 C and 101.3 kPa

Match each term with its correct definition below.A. solution E. heterogeneous mixtureB. homogeneous mixture F. electrolyteC. solute G. nonelectrolyteD. solvent H. aqueous solution

____ 3. solute dissolved in water

Match the piece of solution lab equipment with its use below.A. graduated cylinder E. buretteB. wash bottle F. balanceC. Erlenmeyer flask G. volumetric flaskD. pipette H. stopper

____ 4. controls the volume of solution being delivered during acid-base titrations

Match the following terms with the correct statement below.A. base E. strong acidB. dissociation F. weak acidC. acid G. percentage ionizationD. ionization H. conductivity

____ 5. substance that ionizes almost completely in water to form hydronium ions

Match the following substances with their approximate pH values below.A. battery acid E. lyeB. seawater F. antacid solutionC. blood G. vinegarD. soft drink H. normal rain

____ 6. 8.5

Match the acids or bases with the products that contain them.

A. lye E. milk of magnesiaB. slaked lime F. rust removerC. muriatic acid G. baking sodaD. vinegar H. car batteries

____ 7. sodium hydroxide

Match the following terms with the correct statement below.A. qualitative analysis E. limiting reagentB. quantitative analysis F. excess reagentC. flame test G. forensic chemistD. spectrophotometer H. diagnostic tests

____ 8. reactant present in more than the required quantity for a complete reaction

Short Answer

1. Explain, in your own words, how and why ionic bonding occurs.

2. Use a Lewis diagram to explain the formula for Na2O.

3. What are the three types of motion for particles?

4. Manipulate the following formula to isolate the variable P2.P1V1 = P2V2

5. Identify five careers where a knowledge of compressed gases and the safety precautions associated with these gases would be an asset.

6. Why is dilution important as it relates to commercial products?

7. A sample of well water is thought to contain a high concentration of iron. What solution could you use to obtain a positive precipitate test for the dissolved iron?

8. Balance the following equation: Bi2O3(s) + H2(g) Bi(s) + H2O(g)

9. Sketch the pH curve for a reaction between 10.0 mL of 1.00 mol/L strong acid with 1.00 mol/L strong base.

Problem

1. How much water must be added to 600 mL of a 1.5 mol/L CaCl2 solution to make a solutions with a concentration of 1.0 mol/L?

2. Standard solutions of sodium oxalate, , are required for certain types of chemical analyses. If 8.5 g of sodium oxalate is dissolved in 500 mL of distilled water, calculate the concentration of the sodium ion and the concentration of the oxalate ion, C2O4

2-(aq), dissolved in this solution.

3. The maximum quantity of oxygen that dissolves in water at 0 C is 14.7 ppm and at 25 C, it is 8.7 ppm. Calculate the difference in the mass of oxygen that can be dissolved in a fish tank containing 75 L of water at the two temperatures.

4. The hydronium ion concentration in beer is 3.12 10–5 mol/L. Calculate the pH of beer.

5. Black gunpowder is a mixture of chemicals, including potassium nitrate. A barrel-full of gunpowder contains 1245 g of KNO3(s) and an excess of the other reactants. If this barrel of gunpowder explodes, what is the total volume of all the gases produced? Assume a temperature of 350 C and a pressure of 2000 kPa. The unbalanced equation for the reaction is:

6. A titration was performed on a 10.00 mL sample of water taken from an acidic lake. If it took 8.66 mL of 0.0512 mol/L NaOH(aq) to neutralize the sulfuric acid in the lake water sample, calculate the concentration of the sulfuric acid. What is the pH of this lake water?

7. Consider the following balanced equation: 2 Al(s) + 3 Br2(l) 2 AlBr3(s)Determine the mass of aluminium bromide produced when 31.0 g of aluminium is combined with 97.5 g of bromine.

Essay

1. You have been transported to another dimension where the value of absolute zero is different. You must discover the new value with the same equipment that Lord Kelvin had at his disposal. The following data were collected for an ideal gas that was cooled at constant pressure. Graph the data and determine the new value for absolute zero in this dimension. Determine the freezing point of water and the boiling point of water on this new temperature scale. (Create a name and unit for the new temperature scale.) Explain why this temperature is considered a theoretical point only.

Pressure 1 Pressure 2 Pressure 3

T1 V1 T2 V2 T3 V3

–25 25 –25 150 –25 225

0 50 0 200 0 300

100 100 100 400 100 600

2. Briefly outline some of the advantages of performing chemical reactions in aqueous solution as opposed to using pure substances. Provide theoretical reasoning wherever possible.

3. The labels have fallen off of five beakers. Create an experimental design that could help you identify the 0.1 mol/L solutions as , , , , and .

4. When gasoline is burned in an internal combustion engine the temperature is high enough to cause chemical reactions that damage the environment. Below is a short list of chemical reactions. Using these chemical equations, describe how hydronium ion is formed.N2(g) + O2(g) 2NO(g)2NO(g) + O2(g) 2NO2(g)2NO2(g) + H2O(g) HNO3(aq) + HNO2(aq)

5. Plan a lab for testing the stoichiometric method using the precipitation reaction of lead(II) nitrate with sodium chloride. Including the design, materials list, and Procedure. Explain how you could decide if your results are acceptable.

6. A chemist is analyzing the mass of ASA in a commercial Aspirin® tablet. Write a general Procedure and outline the Analysis.

Chem 20 Review QuestionsAnswer Section

MODIFIED TRUE/FALSE

1. ANS: T PTS: 1 REF: KOBJ: 3.3 | 3.4 LOC: 20-A2.9k

2. ANS: F, higher

PTS: 1 REF: K OBJ: 3.4 | 3.5 LOC: 20-A1.6k | 20-A2.8k3. ANS: T PTS: 1 REF: K

OBJ: 3.4 LOC: 20-A2.7k4. ANS: F

two2

PTS: 1 REF: K OBJ: 3.2 LOC: 20-A2.3k5. ANS: T PTS: 1 REF: K

OBJ: 4.2 LOC: 20-B1.3k6. ANS: F, Nitrogen

PTS: 1 REF: K | STS OBJ: 4.1 LOC: 20-B1.2sts7. ANS: F, uses

PTS: 1 REF: K OBJ: 5.2 LOC: 20-C1.3k8. ANS: F, dynamic equilibrium

PTS: 1 REF: K OBJ: 5.5 LOC: 20-C1.10k9. ANS: F, hydroxide ions

PTS: 1 REF: K OBJ: 6.4 LOC: 20-C2.9k10. ANS: T PTS: 1 REF: K

OBJ: 6.2 LOC: 20-C2.3k | 20-C2.4k11. ANS: F, colour

PTS: 1 REF: K OBJ: 6.3 LOC: 20-C2.6k12. ANS: F, cyanide ion

PTS: 1 REF: K OBJ: 6.4 LOC: 20-C2.8k13. ANS: T PTS: 1 REF: K

OBJ: 6.4 LOC: 20-C2.7k14. ANS: T PTS: 1 REF: K

OBJ: 7.1 LOC: 20-D1.4k15. ANS: T PTS: 1 REF: K

OBJ: 7.2 LOC: 20-D2.4k16. ANS: F, precipitation

PTS: 1 REF: K OBJ: 8.2 LOC: 20-D2.1k17. ANS: F, titrant

PTS: 1 REF: K OBJ: 8.4 LOC: 20-D2.5k18. ANS: T PTS: 1 REF: K

OBJ: 8.4 LOC: 20-D2.7k19. ANS: F, yellow to blue

PTS: 1 REF: K OBJ: 8.5 LOC: 20-D2.6k

MULTIPLE CHOICE

1. ANS: C PTS: 1 REF: K | S OBJ: 3.1LOC: 20-A2.4k | 20-A2.2s

2. ANS: D PTS: 1 REF: K OBJ: 3.4LOC: 20-A2.7k | 20-A2.8k

3. ANS: C PTS: 1 REF: K OBJ: 3.3LOC: 20-A2.5k | 20-A2.6k

4. ANS: B PTS: 1 REF: K OBJ: 3.3LOC: 20-A2.5k | 20-A2.6k

5. ANS: A PTS: 1 REF: K OBJ: 3.1 | 3.5LOC: 20-A1.1k | 20-A1.5k | 20-A2.1k | 20-A2.2k

6. ANS: C PTS: 1 REF: K | S OBJ: 3.1 | 3.2LOC: 20-A2.4k

7. ANS: A PTS: 1 REF: K | S OBJ: 4.1LOC: 20-B1.2k

8. ANS: B PTS: 1 REF: K OBJ: 5.1LOC: 20-C1.1k

9. ANS: C PTS: 1 REF: K OBJ: 5.3LOC: 20-C1.6k

10. ANS: D PTS: 1 REF: K OBJ: 5.5LOC: 20-C1.1k | Review

11. ANS: B PTS: 1 REF: K OBJ: 6.5LOC: 20-C2.1k | 20-C2.10k

12. ANS: B PTS: 1 REF: K OBJ: 6.2LOC: 20-C2.5k

13. ANS: A PTS: 1 REF: K OBJ: 6.5LOC: 20-C2.2k

14. ANS: D PTS: 1 REF: K | S OBJ: 6.3LOC: 20-C2.6k | 20-C2.3s

15. ANS: C PTS: 1 REF: K OBJ: 6.5LOC: 20-C2.11k

16. ANS: D PTS: 1 REF: K | S OBJ: 7.1LOC: 20-D1.2k | 20-D1.2s

17. ANS: C PTS: 1 REF: K | S OBJ: 8.4LOC: 20-D2.1s | 20-D2.7k

18. ANS: A PTS: 1 REF: K | STS OBJ: 8.4LOC: 20-D1.5k | 20-D1.1sts

COMPLETION

1. ANS: electronegativity

PTS: 1 REF: K OBJ: 3.1 | 3.3 LOC: 20-A1.3k2. ANS: polar covalent

PTS: 1 REF: K OBJ: 3.3 LOC: 20-A2.10k3. ANS:

four, larger4, larger

PTS: 1 REF: K | S OBJ: 4.1 LOC: 20-B1.4k | 20-B1.3s4. ANS: solubility

PTS: 1 REF: K OBJ: 5.5 LOC: 20-C1.9k5. ANS: biomagnification

PTS: 1 REF: STS OBJ: 5.3 LOC: 20-C1.4sts6. ANS: natural

PTS: 1 REF: STS OBJ: 7.1 LOC: 20-D2.1sts7. ANS: Filtration

PTS: 1 REF: K | S OBJ: 7.2 LOC: 20-D1.1k | 20-D1.1s

MATCHING

1. ANS: I PTS: 1 REF: K OBJ: 4.1LOC: 20-B1.2s

2. ANS: H PTS: 1 REF: K OBJ: 4.1 | 4.2LOC: 20-B2.4k

3. ANS: H PTS: 1 REF: K OBJ: 5.1 | 5.2 | 5.5LOC: 20-C1.1k | 20-C1.4k

4. ANS: E PTS: 1 REF: K OBJ: 5.4LOC: 20-C1.11k

5. ANS: E PTS: 1 REF: K OBJ: 6.4 | 6.5LOC: 20-C2.7k | 20-C2.8k | 20-C2.10k

6. ANS: B PTS: 1 REF: STS OBJ: 6.1LOC: 20-C2.1sts | 20-C2.2sts

7. ANS: A PTS: 1 REF: STS OBJ: 6.1 | 6.2LOC: 20-C2.1sts | 20-C2.2sts

8. ANS: F PTS: 1 REF: K OBJ: 8.1LOC: 20-D1.3k

SHORT ANSWER

1. ANS:Atoms are more stable when they have eight valence electrons. To form a stable octet, nonmetals tend to gain electrons from metals and become anions whereas metals tend to lose electrons to nonmetals and become cations. The two oppositely charged ions attract each other. The electrostatic attraction of oppositely charged ions is called an ionic bond.

PTS: 1 REF: K OBJ: 3.3 | 3.5 LOC: 20-A1.5k | 20-A1.6k2. ANS:

Sodium forms an ion with a 1+ charge and oxygen forms an ion with a 2– charge. The smallest unit with a zero charge requires two sodium ions and one oxide ion.

PTS: 1 REF: K | S OBJ: 3.1 | 3.5 LOC: 20-A1.4k3. ANS:

translational, rotational, and vibrational motions

PTS: 1 REF: K OBJ: 4.1 LOC: 20-B1.1k4. ANS:

PTS: 1 REF: S OBJ: 4.1 LOC: 20-B1.4k5. ANS:

Possible answers include anaesthesiologist, car designer, diver, firefighter, gas station attendant, barbecue salesperson, mechanic, scientist, and respiratory technician.

PTS: 1 REF: STS OBJ: 4.1 | 4.2 | 4.3 | 4.4LOC: 20-B1.1sts | 20-B1.2sts

6. ANS:Commercial products are purchased in concentrated form in smaller containers. People can dilute them according to their needs.

PTS: 1 REF: K | STS OBJ: 5.4 LOC: 20-C1.11k | 20-C1.1sts7. ANS:

any hydroxide, carbonate, phosphate, or sulfate solution

PTS: 1 REF: K OBJ: 5.5 LOC: 20-C1.1k | 20-C1.1s8. ANS:

Bi2O3(s) + 3 H2(g) 2 Bi(s) + 3 H2O(g)

PTS: 1 REF: K OBJ: 7.1 LOC: 20-D1.2k

9. ANS:

PTS: 1 REF: K | S OBJ: 8.5 LOC: 20-D2.5k | 20-D2.3s

PROBLEM

1. ANS:

The volume of water that must be added is 300 mL.

PTS: 1 REF: K OBJ: 5.4 LOC: 20-C1.7k2. ANS:

The sodium ion concentration is 0.25 mol/L.

The oxalate ion concentration is 0.13 mol/L.

PTS: 1 REF: K OBJ: 5.3 LOC: 20-C1.6k | 20-C1.8k3. ANS:

The difference in the mass of oxygen that can be dissolved at the two temperatures is 450 mg.

PTS: 1 REF: K OBJ: 5.3 | 5.5 LOC: 20-C1.5k | 20-C1.6k | 20-C1.9k4. ANS:

The pH of beer is 4.506.

PTS: 1 REF: K OBJ: 6.2 LOC: 20-C2.3k5. ANS:

The total volume of all the gases produced in the explosion is 63.8 L.

PTS: 1 REF: K OBJ: 7.2 | 7.3 LOC: 20-D1.5k6. ANS:

10.00 mL 8.66 mLc 0.0512 mol/L

or

The sulfuric acid concentration in the lake is 2.22 10–2 mol/L.

Assuming the ionization reaction:H2SO4(aq) + H2O(l) H3O+(aq) + HSO4(aq)

The pH of the lake water is 1.654.

PTS: 1 REF: K OBJ: 7.4LOC: 20-D1.1k | 20-D1.2k | 20-D1.5k | 20-D2.3k

7. ANS:Calculate the chemical amount of bromine needed to react completely with 31.0 g of aluminium.

There is not enough Br2 available for 31.0 g of aluminium to react completely. Therefore, bromine is the limiting reagent.

The mass of aluminium bromide produced is 108.5g.

PTS: 1 REF: K OBJ: 8.2 | 8.3 LOC: 20-D2.2k | 20-D1.5k

ESSAY

1. ANS:Graph 1:

Graph 2:

Graph 3:

The volume is zero when the temperature reaches –100 C. The freezing point of water is 0 + 100 = 100 (in a unit that the student chooses). The boiling point is 100 + 100 = 200 units. Absolute zero is a theoretical point because it assumes gases behave ideally at low temperatures. Real gases condense (liquefy) at low temperatures. Molecules would have to completely stop moving (cease all vibrational, rotational, and translational motion). Real gas molecules are not dimensionless points, therefore, their volume cannot be neglected in calculations. When molecules are brought close together, they have a greater attraction and tend to react to form crystals (hydrogen bonding in ice formation).

PTS: 1 REF: K | S OBJ: 4.1LOC: 20-B1.4k | 20-B1.1s | 20-B1.2s | 20-B1.3s

2. ANS:Many chemical reactions involving ionic compounds only take place in solution because the ions can only react once they dissociate in water.Water may make the reaction safer because it dilutes the reactants to a lower concentration so that less chemical reacts.The water solvent can either absorb energy from the reaction or provide energy to the reaction, which allows the collection of information about the reaction and controls heat flow to and from the reaction.Solutions are generally easier and safer to handle and measure than solids, as the quantities are larger. Furthermore, particles are less likely to become airborne and be inhaled, which may be hazardous.

PTS: 1 REF: K OBJ: 5.1 | 5.4 | 5.5 LOC: 20-C1.1k | 20-C1.2k3. ANS:

- est a sample of each solution with litmus paper, a conductivity meter, and a pH meter.- Sodium chloride solution would not change the litmus paper, would show high

conductivity, and have a pH of 7.- Sodium carbonate solution would turn the litmus paper blue, show moderately high

conductivity, and have a pH of 8.- Sulfuric acid solution would turn the litmus paper red, show high conductivity, and have

a pH of around 0.7.

- Hydrofluoric acid solution would turn the litmus paper red, show low conductivity, and have a pH of 2.

- Potassium hydroxide solution would turn the litmus paper blue, show high conductivity, and have a pH of 13.

PTS: 1 REF: K | S OBJ: 6.1 | 6.2 | 6.5 LOC: 20-C2.1s | 20-C2.2k | 20-C2.6k4. ANS:

-nitrogen gas and oxygen gas combine forming nitrogen monoxide-nitrogen monoxide combines with oxygen forming nitrogen dioxide-nitrogen dioxide combines with water forming nitric and nitrous acid-nitric acid is a strong acid completely dissociating forming hydronium ion-nitrous acid is a moderately strong acid involved in an equilibrium forming hydronium ion

PTS: 1 REF: STS OBJ: 6 LOC: 30-D1.1sts5. ANS:

DesignThe following reaction will be carried out, with sodium chloride as the limiting reagent.Pb(NO3)2(aq) + 2 NaCl(aq) PbCl2(s) + 2 NaNO3(aq)The mass of the dried precipitate will be measured, and compared to the theoretical yield that is predicted using the stoichiometric method.

Materialseye protectionlaboratory apronthree 150 mL beakerstwo 25 mL graduated cylinders0.1 mol/L Pb(NO3)2(aq)0.1 mol/L NaCl(aq)distilled water in dropper bottleglass stirring rodfilter funnelfiltration apparatusfilter paperlaboratory balance

Procedure1. Collect approximately 30.0 mL of each of lead(II) nitrate and measure out 25.0 mL into

a graduated cylinder.2. Repeat with sodium chloride, using a clean beaker and graduated cylinder.3. Pour both solutions into a beaker, being careful to completely transfer all the solution by

rinsing each graduated cylinder. Stir the contents of the beaker until completely mixed.4. Measure the mass of a dry filter before preparing it for filtration.5. Filter the solution, making sure to wash the contents of the beaker into the filter paper.6. Allow the filter paper and precipitate to dry, taking care not to allow any precipitate to

be lost.7. Measure the mass of the precipitate and filter paper.

Calculate the theoretical yield and actual yield of precipitate. Use these two values to calculate the percent yield. In general, if the percent yield is within 10% of the expected yield, the stoichiometric method is supported.

PTS: 1 REF: K | S OBJ: 7.2LOC: 20-D2.3s | 20-D1.1s | 20-D1.3s | 20-D1.5k

6. ANS:Procedure1. Obtain a standardized NaOH solution. Load a burette with this solution.2. Use a mortar and pestle to crush a commercial Aspirin tablet.3. Dissolve the crushed tablet in some methanol in an Erlenmeyer flask.4. Titrate the ASA solution with the standardized NaOH using a phenolphthalein indicator.5. Repeat steps 2 to 4, with different Aspirin® tablets, until consistent results are obtained

for at least three tablets.Analysis1. From the concentration and volume of NaOH required, calculate the chemical amount of

NaOH needed to neutralize the ASA.2. Research the molar mass of ASA.3. Use the chemical amount of NaOH, the mole ratio of NaOH to ASA, and the molar

mass of ASA to calculate the mass of ASA.4. Compare the calculated mass of ASA to the mass reported on the commercial tablet

bottle.

PTS: 1 REF: K | S OBJ: 8.4 | 8.5 LOC: 20-D1.5k | 20-D2.6k | 20-D1.1s