Name___________________________________
Exam 2
CHEM 101, Winter 07 (100 points)
General Instructions:
1) Please write your name on every page
2) There are two parts on the exam, a multiple choice and problem -solving part. For problems with numeric answer, please
cirlce your final answer
3) Good luck!
MULTIPLE CHOICE. Choose the one alternative that best completes the statement or answers the question.
1) (4 pts) How many moles of K2 SO4 are in 15.0 g of K2 SO4 ?
1)
A) 2.61 x 103 moles
B) 0.111 moles
C) 0.119 moles
D) 0.0861 moles
E) 0.172 moles
2) (4 pts) What is the molar mass of Mg 3 (PO4 )2 , a substance formerly used in medicine as an
antacid?
2)
A) 150.3 g
B) 214.3 g
C) 118.3 g
D) 71.3 g
E) 262.9 g
3) ( 4 pts) A cheeseburger from a fast food restaurant contains 19 g of fat, 20 g of carbohydrate, and
28 g of protein. How many kcal of energy does the cheeseburger contain? (The accepted caloric
values for foods are 4.0 kcal/g for carbohydrate, 9 kcal/g for fat, and 4 kcal/g for protein.) Report
the answer to 2 significant figures.
A) 360 kcal
B) 280 kcal
C) 70. kcal
D) 17 kcal
E) 630 kcal
1
3)
4) In which of the following would the particles move most rapidly?
4)
A) water at 20°C
B) steam at 110°C
C) ice at 0°C
D) boiling water
E) ice at -20°C
5) Which of the following is a physical property of both liquids and gases?
5)
A) has its own shape
B) has randomly arranged particles
C) has strong interactions between its particles
D) has a definite volume
E) has large spaces between molecules
6) The energy stored in the chemical bonds of a carbohydrate molecule is
6)
A) specific heat.
B) work.
C) kinetic energy.
D) a calorie.
E) potential energy.
7) Which of the following quantities is NOT required to calculate the amount of heat energy required
to heat water from 25°C to 55°C?
7)
A) the specific heat of water
B) the mass of the water sample
C) the final temperature
D) the heat of vaporization for water
E) the initial temperature
8) Which of the following gives the balanced equation for this reaction?
K3 PO4 + Ca(NO3 )2 → Ca3 (PO4 )2 + KNO3
A) 2 K3 PO4 + Ca(NO3 )2 → Ca3 (PO4 )2 + 6KNO3
B) KPO 4 + CaNO3 + KNO3
C) 2K3 PO4 + 3Ca(NO3 )2 → Ca3 (PO4 )2 + 6KNO3
D) K3 PO4 + Ca(NO3 )2 → Ca3 (PO4 )2 + KNO3
E) K3 PO4 + Ca(NO3 )2 → Ca3 (PO4 )2 + 3KNO3
2
8)
9) What is oxidized and what is reduced in the following reaction?
9)
2Al(s) + 3Br2 (g) → 2AlBr3 (s)
A) AlBr3 is oxidized and Al is reduced.
B) AlBr3 is reduced and Br2 is oxidized.
C) AlBr3 is reduced and Al is oxidized.
D) Al is oxidized and Br2 is reduced.
E) Al is reduced and Br2 is oxidized.
10) A diver exhales a bubble with a volume of 250 mL at a pressure of 2.4 atm and a temperature of
15°C. What is the volume of the bubble when it reaches the surface where the pressure is 1.0 atm
and the temperature is 27°C?
10)
A) 110 mL
B) 1100 mL
C) 630 mL
D) 580 mL
E) 100 mL
11) Which of the following molecules can form hydrogen bonds?
11)
A) CH4
B) HI
C) BH3
D) NaH
E) NH3
12) Water is a polar solvent and hexane (C6 H14) is a nonpolar solvent. Which of the following
correctly describes the solubility of the solute?
A) CaCl2 , soluble in hexane
B) octane, soluble in water
C) CCl4 , soluble in water
D) NaHCO3 , soluble in water
E) mineral oil, soluble in water
3
12)
13) Which one of the following compounds will NOT be soluble in water?
13)
A) LiNO3
B) NaOH
C) MgCl2
D) PbS
E) K2 SO4
14) How many milliliters of a 25% (m/v) NaOH solution would contain 75 g of NaOH?
14)
A) 25 mL
B) 3.0 x 102 mL
C) 33 mL
D) 19 mL
E) 75 mL
15) Indicate the major type of molecular interaction expected of each of the following:
H-Br
I-I
NH3
A) Hydrogen bonding
dipole-dipole
dispersion forces
B) Ionic bond
dispersion forces
dipole-dipole
C) Dipole-dipole
dispersion forces
hydrogen bonding
D) Dispersion forces
ionic bond
hydrogen bonding
E) Dipole-dipole
hydrogen bonding
ionic bond
Proceed to the next pages and the problem solving part ofthe exam.
4
15)
1. (15 pts, 3 pts each) Aqueous magnesium chloride reacts with aqueous silver nitrate to
form solid silver chloride and aqueous magnesium nitrate.
a. Write the balanced molecular and net ionic equations of this reaction.
Molecular Equation: ______________________________________________________________
Net Ionic Equation: ______________________________________________________________
b. How many grams of silver chloride can be produced from 2.00 grams of silver
nitrate?
c. How many grams of magnesium chloride do we need to make 2.5 grams of
silver chloride?
d. What mass of silver chloride can be produced from 250.0 mL of 0.1M
solution of silver nitrate and 150.0 L of 0.5M solution of magnesium chloride?
e. If the actual amount of silver chloride made in part d is 2.50 grams, what is
the percent yield?
2. (5 pts, 2.5 each) Calculate the concentration of CaCl2 in part A and grams of CaCl2
in part B.
a. If we diluted 130.0 mL of 0.50 M CaCl2 to a volume of 250.0 mL, what is the
new concentration of CaCl2?
b. What mass of CaCl2 is required to prepare 150.0 mL of a 0.200 M solution of
CaCl2?
3. (5 pts) If 11.2 L of oxygen at STP reacts with 20.0 g of magnesium to produce
magnesium oxide, how many grams of magnesium oxide are made?
4. (5 pts) When sensors in a car detect a collision, they cause the reaction of sodium
azide, NaN3, which generates nitrogen gas (balanced chemical reaction shown below)
to fill the air bags within 0.03 seconds.
2NaN3(s) Æ 2Na(s)
+ 3N2(g)
How many liters of N2 gas are produced at STP if the air bag contains 132g NaN3?
5. (5 pts, 2.5 each)) Using the values for the heat of fusion, specific heat of water,
and/or heat of vaporization, calculate the heat energy involved in each of the
following processes.
a. Amount of heat needed to warm 20.0 g of water at 10oC to 85oC
b. Amount of heat needed to melt 30.0 g of ice at 0cC, warm the resulting liquid
100oC, and than vaporize at 100oC
6. (5 pts) It is a hot day and you wanted to treat yourself with a cup of cold water. The
temperature of the water you poured were at room temperature (21oC). You are added
a 35-g piece of ice at 0oC to your water. All of the ice melts and the temperature of
the water decreases to 0oC. How many grams of water were in the sample?
Answer Key
Testname: MIDTERM II
1) D
2) E
3) A
4) B
5) B
6) E
7) D
8) C
9) D
10) C
11) E
12) D
13) D
14) B
15) C
5