chem 16 3rd long exam reviewer

7/25/2019 Chem 16 3rd Long Exam Reviewer

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UP Chemical Societyin partnership with UP 49ersbrings you

Chemistry Review SeriesChem 16 3rdLong Exam

I.Modified True or False.Write TRUE if the statementis correct. Otherwise, write FALSE then change theunderlined word(s) to make the statement true.

1. Gas molecules possess volume but have negligible mass.2. A solution contains 1.8 x 10-9 M [OH-]. This solution istherefore basic.3. Nuclear binding energy is the energy absorbed whennucleons fuse together into a nucleus.4. Nuclear reactions, in general, give off much more energythan chemical reactions.

5. The gas constant varies on two components of theIdeal Gas Equation: volume and temperature.6. Alloys are solutions with a metal solute and liquid solvent.7.The pH of a 0.20 solution of HCN (Ka= 4.9 x 10-10) isequal to 5.

8. A solution is a homogeneous mixture, and can bedescribed as either dilute, a solution with minimal soluteoriginally, and as concentrated, a solution with themaximum.9. Generally, an increase in temperature increases thesolubility of gases in water.10. Pressure changes do not affect the solubility of liquidsand solids, but affects the solubility of gases as described byHenrys Law.11. Hexane and octane will form an ideal solution, due totheir IMFAs being quite similar.12. Increased moles of H2at 300 K and 1 atm results to gascompression.13. When ice cubes are made by placing water in a tray in afreezer, energy is removed from the water molecules, whichgradually slow down.14. When ethanol is mixed with acetone, this results to adecrease in temperature and an increase in volume of thesolution.

II. Cause and Effect.Identify the effect of the conditionon the indicated parameter. Write increase, decrease, no effect,orindeterminate.

Condition Parameter

1. 0.8 molal rock salt solutionwas used instead of 0.3 molal.

Boiling point elevation

2. Presence of air bubbles ineudiometer

%error betweencalculated and pre-

weighed Mg

3. The volumetric flask usedto mix methanol and waterwasnt dry.

Temperature; Finalvolume of solution

4. HBr was added to thegumamela extract instead ofHCl.

Color change

5. The water used to dilute0.1M HCl was contaminated

with some 0.1 M NaOH

pH change as comparedto uncontaminated

water

III. Multiple Choice.Write the letter of your answer.

1. According to the Bronsted-Lowry theory, which of thefollowing is correct (given the chemical equation below):

NH3+ H2PO4-NH4++ HPO42-a) NH4- acts as the conjugate base of NH3b) In the reverse reaction, H2PO4- acts as the

conjugate acidc) HPO42- acts as the conjugate acid of H2PO4-d) In the forward reaction H2PO4- acts as theconjugate base

2. Glycerin (C3H8O3) is a nonvolatile nonelectrolyte with adensity of 1.26 g/mL at 25C. A solution was made bymixing 50.0 mL of glycerin to water (500.0 mL). Calculatethe vapor pressure of the solution at 25C if the vaporpressure of pure water at 25C is 23.8 torr, and its density is1.00 g/mL.

a) 23.7 torrb) 23.8 torrc) 23.9 torrd) 24.0 torr

For numbers 3 and 4, refer to the diagram below:

3. Point T is where ______a) supercritical fluid is createdb) the three phases coexistsc) intermediates are formedd)the phases are isolated from each other

4. Supercritical fluid exists in Point __a) A c) Cb) B d) D

A

B


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5. Which of the following nuclides would you expect to bestable and why?

a) 88Sr, because it has an average mass of 87.6b) 118Cs, because it has an average mass of 132.9c) 30S, because it has an average mass of 32.1d) 214Po, because it has an atomic number of 84

6. Given 500 mL of a sucrose solution in 9.88 ppm, calculatethe volume (in mL) of the solution in which 0.75 grams of

sucrose can be found.a) 0.0821 mLb) 0.0653 mLc) 0.0759 mLd) 0.092 mL

7. Mo He Tc _____ a) e b) e+ c) 2 n d) n

8. The average osmotic pressure of blood is 7.7atm at 25C.What molarity of glucose (C6H12O6) will be isotonic withblood? Note that glucose is a nonelectrolyte.

a) 0.30 Mb) 0.31 Mc) 0.32 Md) 0.43 M

9.The following are the formulas of the gas laws. Identifythe incorrect equation:

a) Boyles Law: = b) Charless Law:

=

c)Avogadros Law: = d) Ideal Gas Equation: =

10. Which of the following is true?a) Absorption of an electron by the nucleus is

followed by X radiation.b) Atomic number decreases by 4 upon emission of

alpha particle.c) Atomic number decreases by 4 upon emission of

alpha particle.d) Beta decay involving conversion of a proton to

a neutron inside the nucleus emits - particle.

11. Silver nitrate, AgNO3, reacts with sodium chloride asindicated by the following equation. What mass of NaCl

would be required to react with 200 mL of 0.200 M AgNO3solution?

AgNO3+ NaCl AgCl + NaNO3a)

0.117 gb) 1.17 gc) 2.34 gd) 4.68 g

12. Given the following acids and corresponding pKa, whawould be the most basic (strongest) conjugate base? DAcid pKaH2O 15.7CH3CH2OH 16(CH3)3COH 18CH3COCH3 19.2

a) HO-

b) CH3CH2O-c) (CH3)3CO-

d) -CH2COCH313.What is the vant Hoff factor of a 0.10 mHF(aq)solution

with a freezing point depression of 0.2010C? (Kf= 1.860C/m)

a) 1.07b) -1.07c) 1.08d) -1.08

14. Dissolution of carbon dioxide in water yields

a) solution with separate gaseous and liquid phasesb) solution that can change red to blue litmus paperc) solution of pH less than 7.d) none because CO2cannot be dissolved in water

IV. Problem Solving.

1. Container X holds 5.35 grams of He, in a volume of 20.2L. Container Y holds 8.66 grams of H2, in its volume of 25.0L. Lastly, container Z holds 0.45 moles of gas AlDub, in a15.7 L volume. Calculate for (a) partial pressures of each gas(b) the total pressure if Containers X and Y are added, and(c) the molar mass of gas AlDub if its density is 1.45 g/L.

2. Madame Curie won the 1911 Nobel Prize for isolatingradium. Radium-226 has a half-life of 1662 years andundergoes alpha decay.

a) Write the equation for the decay process.b) If she had 1.20 g of Radium-226 in her lab in 1911

what would be its mass in 2010?

3. A sucrose-water solution is produced by dissolving 2.45grams of sucrose in water to produce a 75-mL solution withdensity 0.584 g/mL. (MWsucrose= 342.3 g) Calculate for themass-volume percent, molarity, and molality.

4. How many milliliters of 12 M hydrochloric acid solutionnecessary to consume 80 mg of magnesium metal? Calculate%error if 1.87 mmol Mg was found to have reacted. (MWM= 24.3050 g/mol; MWHCl= 36.4606 g/mol)

5. Nyemi prepared a 0.10 M solution of formic acid(HCOOH). When he measured its pH at 25C, it read as2.38. What is the Kaof the acid at this temperature? What isits percent ionization?


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Answer Key:I. True or False1. FALSE mass, volume 11.TRUE2. FALSE acidic 12. FALSE gas expansion3. FALSE released 13.TRUE4. TRUE 14. TRUE5. FALSE volume & pressure6. FALSE metal solvent7. TRUE8. FALSE concentrated, dilute9. FALSE decreases10. TRUE

II. Cause and Effect1. Increase 4. No effect2. Decrease 5. Increase3. Increase; Increase 6. Increase

III. Multiple Choice1. B 6. A 11. C2. B 7. C 12. D3. B 8. B 13. C4. C 9. B 14. C5. A 10. A

IV. Problem Solving

1. (a) Partial Pressures

PV=nRT

P = nRTV =(5.35 x 1 mol4.0026 g)0.0821318.15

20.2P He = 1.728 atm

P = nRTV =(3.66 x 1 mol2.016 g)0.0821318.15

20.2P H = 2.348 atm

P =nRT

V =0.450.0821313.15

20.2P AlDub=0.573 atm(a)Total Pressure of X and Y

P = nRTV =1.337 mol 1.8150.0821318.15

20.2 P = 4.076 atm(b)

MM of AlDub

MM = DRTP =1.450.0821313.15

0.573 MM = 65.06g mol 2. a) b) The half-life decay formula is: A = A 2

h A = resulting amount after t yearsAo= initial amounth = half-life of the substancet = time in years

A = 1 . 2 0 2 A = 1 . 2 0 2 = . 3. (a) Mass-volume percent

Mass vol percent= mass of solutevolume of solution x 100

Mass vol percent= 2.45 grams sucrose75mL solution x 100Mass vol percent=3.27%(b) Molarity

Molarity= moles of solutevolume of solution

M =2.45 grams x 1 mol342.3 g

0.075 L solution = 0.0954 M

(c) Molality

Mass of solution = 75 mL x mL0.584 gMass of solution = 128.42 gramsMass of HO=128.42 g2.45 gMass of HO=125.97 grams

Molality=2.45 grams x 1 mol342.3 g

0.12597 kg HO Molality=0.05682 m4. a. mL HCl:

=0.080g 1 mol Mg24.3050 g2 mol HCl1 mol Mg1 L HCl solution12 mol HCl 1000 mL1 L = 6.6 mL HCl

b. %error =.[. 24.3050 g ]

. x 100 = 43%

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chem 16 3rd long exam reviewer

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