Name
Chem 250 2nd Semester Exam Review Worksheet
(answers and units are at the end of this worksheet, cross them off as you solve each problem)
1. Round to the correct number of significant figures:
a. (8.54 x 10-3) – (3.41 x 10-4) =
b. 3.40 + 7.34 + 6.45 =
c. 45 x 72 x 132 =
d. 38736 / 4784 =
2. The accepted density for copper is 8.96 g/mL. Calculate the percent error for a measurement of 8.86 g/mL.
3. How many electrons, protons, and neutrons are in the following?
a. Ti-48
b.
132
Cs
55
4. Silver has two isotopes: Ag-107 has a mass of 106.905 amu (52.00%) and Ag-109 has a mass of 108.905 amu (48.00%). What is the atomic mass
of silver?
5. P-32 has a half-life of 14.28 days. How much of a 15.5 g sample of P-32 will remain after 6 half-lives?
6. Given the electron configuration, name the element:
a. 1s22s22p3
b. [Ne]3s23p4
c. Write the electron configuration of magnesium.
d. Write the electron configuration of magnesium ion.
7.
a. Which of the following has the largest atomic radius: N, Sb, As?
b. Which of the following has the smallest atomic radius: Na, Mg, K, Ca?
c. Which of the following has the smallest ionic radius: S, Cl, Se, Br?
d. It can be predicted that silicon will experience a large jump in ionization energy after its _________________ ionization.
8. Write the formula for the ionic compound composed of:
a. cesium and nitride
b. aluminum and bromide
1 c. calcium and carbonate
d. sodium and sulfite
e. ammonium and phosphate
9. Name the following:
a. As2O3
b. N2F4
c. H2Se
d. HClO3
10. What is the molecular geometry of the following:
a. SCl2
b. AlCl3
c. PH3
d. CCl4
e. SF6
11. Polar or nonpolar:
a. NCl3
b. BF3
c. CS2
d. ClF
12. Predict the products (write NR if no reaction):
a. Al + S 
b. C2H6 + O2 
c. NaN3 
d. Ni + MgCl2 
e. Ca + CuBr2 
f. F2 + FeI2 
g. Br2 + CoCl2 
13.
a. How many representative particles are there in 0.250 mol silver?
b. How many moles are there in 1.56 x 10 23 formula units of sodium hydroxide?
c. How many molecules are there in 0.254 mol As2O3?
2 d. How many moles are there in 1.25 x 1015 molecules CO2?
e. How many grams are there in 4.22 x 1015 atoms of U?
f. How many moles of oxygen atoms are contained in 2.50 mol KMnO4?
g. How many moles of Al ions are in 45.0 g aluminum oxide?
h. How many formula units are present in 500.0 g lead(II) chloride?
i. Calculate the mass of 3.62 x 1024 molecules of C6H12O6.
14.
Express the composition of Al2(SO4)3 as the mass percent of its elements (percent composition).
15.
Monosodium glutamate (MSG) is sometimes added to food to enhance flavor. Analysis determined this compound to be 35.5% C,
4.77% H, 8.29% N, 13.6% Na, and 37.9% O. What is the empirical formula for MSG?
16.
Glycerol is a thick, sweet liquid obtained as a byproduct of the manufacture of soap. Its percent composition is 39.12% carbon,
8.75% hydrogen, and 52.12% oxygen. The molar mass is 92.11 g/mol. What is the molecular formula for glycerol?
17.
Carbon dioxide is released into the atmosphere through the combustion of octane (C8H18) in gasoline. Write the balanced chemical
equation for the combustion of octane and calculate the mass of octane needed to release 5.00 mol CO2.
3 18. Chloroform (CHCl3), and important solvent, is produced by a reaction between methane and chlorine:
CH4(g) + 3Cl2(g)  CHCl3(g) + 3HCl(g)
How many g CH4 is needed to produce 50.0 g CHCl3?
19. An alkaline battery produces electrical energy according to this equation.
Zn(s) + 2MnO2(s) + H2O(l)  Zn(OH)2(s) + Mn2O3(s)
a) Determine the limiting reactant if 25.0 g Zn and 30.0 g MnO2 are used.
b) Determine the mass of Zn(OH)2 produced.
20. Pure zirconium is obtained using the two-step Van Arkel process. In the first step, impure zirconium and iodine are heated to produce zirconium
iodide (ZrI4). In the second step, ZrI4 is decomposed to produce pure zirconium.
ZrI4(s)  Zr(s) + 2I2(g)
Determine the percent yield of zirconium if 45.0 g ZrI4 is decomposed and 5.00 g pure Zr is obtained.
21. A sealed flask contains neon, argon, and krypton gas. If the total pressure in the flask is 3.782 atm, the partial pressure of Ne is 0.435 atm, and the
partial pressure of Kr is 1.613 atm, what is the partial pressure of Ar in torr?
22. Hot-air balloons rise because the hot air inside the balloon is less dense than the cooler air outside. Calculate the volume an air sample will occupy
inside a balloon at 43.0 oC if it occupies 2.50 L at the outside air temperature of 22.0 oC, assuming the pressure is the same at both locations.
4 23. A sample of nitrogen gas is stored in a 500.0 mL flask at 108 kPa and 10.0 oC. The gas is transferred to a 750.0 mL flask at 21.0 oC. What is the
pressure of nitrogen in the second flask?
24. CO is a product of incomplete combustion of fuels. Find the volume that 42 g of CO gas occupies at STP.
25. A 2.00 L flask is filled with propane gas (C3H8) at 1.00 atm and -15.0 oC. What is the mass of the propane in the flask?
26. When heated, solid potassium chlorate (KClO3) decomposes to form solid potassium chloride and oxygen gas. If 20.8 g of potassium chlorate
decomposes, how many liters of oxygen gas will form at STP?
27. What mass of water must be added to 255.0 g NaCl to make a 15.00 percent by mass aqueous solution?
28. How many grams KOH are contained in 64.3 mL 0.0238 M solution?
29. How many mL of 0.400 M HBr solution can be made from 50.0 mL of 8.00 M HBr solution?
5 30. Calculate the molality of a solution that contains 15.7 g NaCl in 100.0 g H2O.
31. Calculate the freezing point and boiling point of 2.75 m NaOH in water.
32. How much heat, in kJ, does a 2000 kg granite boulder absorb as energy from the sun causes its temperature to change from
10oC to 29oC?
33. How much heat is evolved when 1255 g of water condenses to a liquid at 100oC?
34. NO gas and Cl2 gas react according to the equation 2NO + Cl2  2NOCl. Use the following data to determine the rate law for the reaction by
the method of initial rates. Also, calculate the value of the specific rate constant.
Trial
1
2
3
Initial [NO]
0.50
1.00
1.00
Initial [Cl2]
0.50
0.50
1.00
Initial Rate (mol/L-min)
1.90 x 10-2
7.60 x 10-2
15.20 x 10-2
6 35. What mass of octane must be burned in order to liberate 5340 kJ of heat? (ΔHcomb = -5471 kJ/mol)
36. The concentration of reactant A decreases from 0.400 mol/L at time = 0 to 0.384 mol/L at time = 4.00 min. Calculate the average reaction rate
during this time period.
37. Calculate Keq for the following equilibrium when [SO3] = 0.0160 M, [SO2] = 0.00560 M, and [O2] = 0.00210 M.
heat + 2SO3(g) D 2SO2(g) + O2(g)
38. Predict the shift in the equilibrium of the chemical equation (to the left or to the right) in #37 if:
a. the volume increases
b. the pressure increases
c. [O2] decreases
d. [SO3] increases
e. the temperature decreases
Answers: -­‐10.2 2.08 x 10-­‐9 1.67 x 10-­‐6 2.57 x 10-­‐4 8.20 x 10-­‐3 4.00 x 10-­‐3 2.59 x 10-­‐1
0.0859 0.152 0.242 0.883 1.12 1.734 2.68 2.69 4.16 5.70 6.72 8.097 10.0 15.77
17.1 17.19 22 22 26 28.12 34 55 55 56.11 71.4 73.0 74.8 77
102.8 107.86 112 1.00 x 103 1080 1445 2830 30,000 4.3 x 105 1.51 x 1023 1.53 x 1023 1.082 x 1024 1s22s22p63s2 1s22s22p6 acid acid AlBr3 Al2S3 bent
CaCO3 Cl C3H8O3 C5H8NO4Na 2C8H18 chloric CoBr2 CO2 16CO2 Cs3N Cu
diarsenic dinitrogen FeF2 fourth H2O 18H2O hydroselenic I2 k[NO]2[Cl2] left
left Mg MnO2 Na Na2SO3 N2 (NH4)3PO4 nitrogen nonpolar nonpolar NR NR 25O2
octahedral planar polar polar pyramidal right right right Sb sulfur
tetrafluoride tetrahedral trigonal trigonal trioxide Units: amu atoms e-­‐ e-­‐ formula units g g g g g g g g
g g kJ kJ kPa L L L L2/(mol2 x min) p+ p+ m mL oC oC mol mol mol mol mol/(L x min) molecules n0 n0 torr % % % % % 7