Final Practice Test Solutions

1. In a double-displacement reaction, hydrogen chloride and sodium hydroxide react to produce sodium chloride. Another product is

a. water. c. hydrogen gas.

b. potassium chloride. d. sodium hydride.

• HCl + NaOH NaCl + H2O

2. The number of atoms in 1 mol of carbon is

a. 5.022 x 1022. c. 6.022 x 1023.

b. 6.022 x 1022. d. 5.022 x 1023.

• 1 mole of anything Avogadro’s number = 6.022 x 1023

3. A prospector finds 39.39 g of pure gold (atomic mass 196.9665 amu). She has

a. 1.204 x 1023 atoms of Au. c. 2.308 x 1023 atoms of Au.

b. 6.022 x 1023 atoms of Au. d. 4.306 x 1023 atoms of Au.

• 39.29 g Au moles Au atoms Au

• 39.29 g Au x 1 moles Au = 0.2 moles Au196.96 g Au

• 0.2 moles Au x 6.022 x 1023 atoms = 1.2 x 1023 atoms Au1 mole

4. The equation AX A + X is the general equation for a

a. decomposition reaction. c. single-displacement reaction.

b. synthesis reaction. d. combustion reaction.

• Decomposition - AX A + X

• Synthesis – A + X AX

• Single – AX + B AB + X

• Double – AX + BY AY + BX

5. How many moles of atoms are in 50.15 g of mercury (atomic mass 200.59 amu)?

a. 0.2500 mol c. 0.1001 mol

b. 0.1504 mol d. 0.4000 mol

• Grams moles

• 50.15 g Hg x 1 mole Hg = 0.25 mole Hg200.59 g Hg

6. The equation 2C2H7OH + 9O 6CO2 + 8H2O is an example of which type of reaction?

a. single-replacement reaction

b. double-replacement reaction

c. combustion reaction

d. decomposition reaction

7. When the equation Fe3O4 + Al Al2O3 + Fe is correctly balanced, what is the coefficient of Fe?

a. 9 c. 6

b. 4 d. 3

• 3Fe3O4 + 8Al 4Al2O3 + 9Fe

8. How many liters of hydrogen gas (H2) are needed to react with CS2 to produce 2.50 L of CH4 at STP?

4H2 + CS2 CH4 + 2H2S

a. 7.50 L c. 10.0 L

b. 2.50 L d. 5.00 L

• 4H2 + CS2 CH4 + 2H2S

• 2.50 L CH4 x 4 L H2 = 10 L H2

1 L CH4

9. For the reaction represented by the equation

SO3 + H2O H2SO4

how many grams of sulfuric acid can be produced from 200. g of sulfur trioxide and 100. g of water?

a. 200. g c. 100. g

b. 245 g d. 285 g

• 200 g SO3 g H2SO4

• 200 g SO3 x 1 mol SO3 x 1 mol H2SO4 x 98 g H2SO4 = 245 g H2SO4

80 g SO3 1 mol SO3 1 mol

• 100 g H2Ox1 mol H2O x1 mol H2SO4 x 98 g H2SO4 = 544 g H2SO4

18 g H2O 1 mol H2O 1 mol

10. Calculate the approximate volume of a 0.600 mol sample of gas at 15.0°C and a pressure of 1.10 atm.

a. 139 L c. 12.9 L

b. 22.4 L d. 24.6 L

• PV = nRT

• P = 1.10 atm

• V = ?

• N = 0.600 mol

• R = 0.0821

• T = 15 C + 273.15 = 288.15 K

• (1.10)V = (0.6)(0.0821)(288.15)

• V = 12.9 L

11. What is the volume, in liters, of 0.500 mol of C3H8 gas at STP?

a. 11.2 L c. 22.4 L

b. 16.8 L d. 0.0335 L

• PV = nRT

• P = 1 atm (at STP)

• V = ?

• N = 0.500 mol

• R = 0.0821

• T = 0 C + 273.15 = 273.15 K

• (1)V = (0.5)(0.0821)(273.15)

• V = 11.2 L

12. Which coefficients correctly balance the formula?

NH4NO2 N2 + H2O

a. 1,2,2 c. 1,1,2

b. 2,1,1 d. 2,2,2

• 1NH4NO2 1N2 + 2H2O

13. For the reaction represented by the equation

N2 + 3H2 2NH3

how many moles of nitrogen are required to produce 18 mol of ammonia?

a. 18 mol c. 9.0 mol

b. 27 mol d. 36 mol

• 18 mol NH3 x 1 mol N2 = 9 mol N2

2 mol NH3

14. For the reaction represented by the equation

2Na + Cl2 2NaCl

how many grams of chlorine gas are required to react completely with 2.00 mol of sodium?

a. 35.5 g c. 141.8 g

b. 70.9 g d. 212.7 g

• 2 mol Na x 1 mol Cl2 x 70.9 g Cl2 = 70.9 g Cl2

2 mol Na 1 mol Cl2

15. How many moles of aluminum are needed to react completely with 1.2 mol of FeO?

2Al(s) + 3FeO(s) 3Fe(s) + Al2O (s)

a. 2.4 mol c. 1.2 mol

b. 0.8 mol d. 1.6 mol

• 1.2 mol FeO x 2 mol Al = 0.8 mol Al 3 mol FeO

16. How many grams of chromium are needed to react with an excess of CuSO to produce 27.0 g Cu?

2Cr + 3CuSO4 Cr2(SO4)3 + 3Cu

a. 18.0 g c. 33.2 g

b. 14.7 g d. 81.5 g

• 27 g Cu mol Cu mol Cr g Cr

• 27 g Cu x 1 mol Cu x 2 mol Cr x 52 g Cr = 14.7 g Cr 63.5 g Cu 3 mol Cu 1 mol Cr

17. What is the molarity of a solution that contains 0.202 mol KClin 7.98 L solution?

a. 0.459 M c. 1.363 M

b. 0.0132 M d. 0.0253 M

• Molarity = moles volume (L)

• M = 0.202 = 0.0267.58 L

18. What is the molarity of a solution that contains 125 g NaCl in 4.00 L solution?

a. 0.535 M c. 31.3 M

b. 2.14 M d. 8.56 M

• Molarity = moles volume (L)

• Volume = 4.00 L

• Moles = ? use grams and convert to moles

• 125 g NaCl x 1 mol NaCl = 2.14 mol NaCl58.5 g NaCl

• 2.14 mol = 0.53 M NaCl4.00 L

19. How many mL of a 2.0M NaBr solution are needed to make 200.0 mL of 0.50M NaBr?

a. 100 mL c. 25 mL

b. 150 mL d. 50 mL

• M1V1 = M2V2

• M1 = 2.0 M

• V1 = ?

• M2 = 0.50 M

• V2 = 200 mL (no need to convert to Liters)

• (2.0) V1 = (0.50)(200)

• V1 = (0.50)(200)(2.0)

• V1 = 50 mL

20. For a process in which ∆H is –298 kJ and ∆S is 100 J/k, calculate the change in the free energy at 0°C.

a. –325 kJ c. –198 kJ

b. –298 kJ d. –271 kJ

• ∆G = ∆H - T∆S

• ∆H = -298 kJ

• ∆S = 100 J Convert to kJ 100/1000 = 0.1 kJ

• T = 0 C Convert to K 0 + 273.15 = 273.15 K

• ∆G = (-298) – (273)(0.1)

• ∆G = -325 kJ

• ∆G = free energy

• ∆H = enthalpy (heat)

• ∆S = entropy (disorder)

21. Which expression defines the change in free energy?

a. ∆H + T∆G c. ∆S – T∆H

b. ∆H + T∆S d. ∆H – T∆S

22. Spontaneous reactions are driven by

a. decreasing enthalpy and decreasing entropy.

b. decreasing enthalpy and increasing entropy.

c. increasing enthalpy and increasing entropy.

d. increasing enthalpy and decreasing entropy.

• Spontaneous reactions Low ∆H and high ∆S

• Non-spontaneous reactions High ∆H and low ∆S

23. How much energy does a copper sample absorb as energy in the form of heat if its specific heat is 0.384 J/(g•°C), its mass is 8.00 g, and it is heated from 10.0°C to 40.0°C?

a. 0.0016 J c. 92.2 J

b. 92.2 J/(g•°C) d. 0.0016 J/(g•°C)

• Q = mc∆T

• M = 8.00 g

• C = 0.384 J/(gC)

• ∆T = Tfinal – Tinitial = 40-10 = 30 C

• Q = (8)(0.384)(30) = 92.2 J

Unit for specific heat!

24. The standard molar enthalpy of vaporization for water is 40.79 kJ/mol. What mass of steam is required to release 500. kJ of energy upon condensation? (Molar mass of water is 18.02 g/mol.)

a. 221 g c. 325 g

b. 1130 g d. 1660 g

• Q = Hv m

• Q = 500 kJ

• Hv = 40.79 kJ/mol

• M = moles (see unit above?)

• 500 kJ = (40.79 kJ/mol)m

• 500 = m = 12.26 moles40.79

• 12.26 moles H2O x 18 g H2O = 220.6 g H2O 1 mol H2O

25. In the reaction represented by the equation

HClO3 + NH3 NH4+ + ClO3

-

, the conjugate base of HClO3 is

a. not shown. c. NH3.

b. NH4+ d. ClO3

-

• Conjugate acid-base pairs • HClO3 and ClO3

-

• NH3 and NH4+

26. The pH of a solution is 9.0. What is its H3O+ concentration?

a. 1 x 10-9 M c. 1 x 10-7 M

b. 1 x 10-5 M d. 9 M

• [H3O+]= [H+]

• pH = -log[H+]

• [H+] = 10-pH

• [H+] = 10-9 = 1 x 10-9

27. What is the pH of a 10–5 M KOH solution?

a. 11 c. 3

b. 9 d. 5

• KOH = base 10-5 = [OH-]

• Kw = [H+] x [OH-]

• Kw = [H+][OH-]

• 1 x 10-14 = 10-9

10-5

• pH = -log[H+]

• -log[10-9] = 9

28. What is the molarity of an HCl solution if 125 mL is neutralized in a titration by 76.0 mL of 1.22 M KOH?

a. 0.455 M c. 0.371 M

b. 0.617 M d. 0.742 M

29. What are the Brønsted-Lowry acids in the following equilibrium reaction?

CN + H O HCN + OH

a. CN-, H2O c. H2O, OH-

b. CN-, OH- d. H2O, HCN

30. Which of the following is the correctly balanced equation for the incomplete combustion of heptene, C7H14?

a. C7H14 + O2 + C7O2 + 7H2 c. 2C7H14 + 21O2 + 14CO + 14H2O

b. C7H14 + 14O + 7CO + 7H2O d. C7H14 + 7O2 + 7CO + 7H2O

31. How many atoms are in 0.075 mol of titanium?

a. 1.2 x 10-25 c. 2.2 x 1024

b. 6.4 x 102 d. 4.5 x 1022

32. In the equation 2KClO3 2KCl + 3O2, how many moles of oxygen are produced when 3.0 mol of KClO3 decompose completely?

a. 4.5 mol c. 1.0 mol

b. 3.0 mol d. 2.5 mol

33. For the reaction represented by the equation 2Fe + O2 2FeO, how many grams of iron(II) oxide are produced from 8.00 mol of iron in an excess of oxygen?

a. 1310 g c. 712 g

b. 71.8 g d. 575 g

1. A

2. C

3. A

4. A

5. A

6. C

7. A

8. C

9. B

10. C

11. A

12. C

13. C

14. B

15. B

16. B

17. D

18. A

19. D

20. A

21. D

22. B

23. C

24. A

25. D

26. A

27. B

28. D

29. D

30. D

31. D

32. A

33. D