Chem2A Test 2
Spring 2015 Name__________________________________________ Score __________/150
*Put your name on BOTH scantron and test paper. Turn in your scantron to the stack with CORRECT COLOR (Yellow or White).
MULTIPLE CHOICE. 3 pts for each choice.
1) The total number of valence electrons in NO2 + is
A) 18
1)
B) 23
C) 17
D) 16
2) Which of the following Lewis structures does NOT fulfill the octet rule?
. .
. .
A) H : O : C : : O :
· · · ·
H
B) H : C :: N :
· ·
. .
C) H : C : : O :
· ·
H
. . · ·
. .
D) : F : C : C : F :
· · · ·
· · · ·
H
H
2)
. . . .
3) How many VSEPR electron groups are on the central atom in the Lewis structure : F : N :: O :
· ·
· ·
A) 4
B) 1
C) 3
D) 2
4) The molecule AXY with three VSEPR electron groups on the central atom A would look like which
one of the following
A)
B)
C)
D) none of the above
. . . .
. .
5) The molecular geometry of the molecule with a Lewis structure as : F : N : F :
· · · · · ·
H
A) tetrahedral
C) trigonal pyramidal
3)
4)
5)
B) linear
D) trigonal planar
6) For a molecule AX3 with four VSEPR electron groups on the central atom A, the bond angle
∠X-A-X is closest to
A) 180°
B) 120°
C) 90°
D) 109.5°
1
6)
7) Using VSEPR theory, predict which of the following triatomic molecules is linear
. . . . . .
. .
. .
. .
. . . .
A) : Cl : O : Cl :
B) H : O : H
C) : O : : C : : O :
D) H : O : I :
· · · · · ·
· ·
· · · ·
. .
8) The molecular geometry of the molecule with a Lewis structure as H : C : : O :
· ·
H
A) linear
C) trigonal pyramidal
8)
B) tetrahedral
D) trigonal planar
9) Which of the following molecules is nonpolar?
A) HCN
B) CO 2
9)
C) H2 O
D) HCl
10) Which one of the following hypothetical molecules is polar? (A and X are two different elements;
△EN ≠ 0)
A) Tetrahedral AX 4
B) Trigonal pyramidal AX 3
C) Linear X-A-X
10)
D) Trigonal Planar AX3
11) Calculate the formula mass of Ca3 (PO4 )2 .
A) 250.82 amu
7)
11)
B) 357.5 amu
C) 310.18 amu
D) 160.00 amu
12) When calculating the moles of CO 2 molecules from the mass of CO 2 , the conversion factor to use
12)
is
A)
12.01 g
1 mole
B)
1 mole
44.01 g
C)
6.022 × 1023
1 gram
D)
1 mole
6.022 × 1023
13) When calculating the number of CO2 molecules from the moles of CO 2 , the conversion factor to
13)
use is
A)
12.01 g
1 mole
B)
1 mole
44.01 g
C)
1 mole
6.022 × 1023
D)
6.022 × 1023
1 gram
14) Alka-Seltzer tablets fizzles when dissolved in water
C6 H8 O7 + 3 NaHCO3 → Na 3 C6 H5 O7 + 3 CO2 + 3 H2 O
14)
Based on this equation, how many moles of C 6 H8 O7 is needed to react with 10.8 moles of
NaHCO 3 (baking soda)?
A) 1.20 mole
B) 10.8 moles
C) 3.60 mole
D) 1.00 mole
15) Which of the following conditions would NOT affect the equilibrium constant of chemical
reactions?
I. the presence of catalyst
II. change in reaction temperature
III. change in concentration(s) of reactants
IV. volume of reactant
A) I
B) II
C) IV
D) III
E) II and III
2
15)
16) The primary reaction in the air bags in our cars is as follows:
2 NaN3 → 2Na + 3N2
16)
Which of the following is the correct ʺsetupʺ for the problem, ʺHow many grams of nitrogen gas
would form when 10.0 g NaN 3 decomposes according to the equation?ʺ A) 10.0 g NaN3 × B) 10.0 g NaN3 × 1 mole NaN3
65.02 g NaN 3
1 mole NaN3
65.02 g NaN 3
× × 3 moles N2
2 mole NaN3
× 3 moles N2
2 moles NaN3
14.01 g N2
1 mole N2
× 28.02 g N2
1 mole N2
1 mole NaN3
1 mole N2
28.02 g N2
C) 10.0 g NaN3 × × × 65.02 g NaN 3 1 mole NaN3 1 mole N2
D) 10.0 g NaN3 × 1 mole NaN3
3 mole N2
28.02 g N2
× × 65.02 g NaN 3 1 mole NaN3 1 mole N2
17)
17) The reaction energy profile as shown below indicates the reaction is _________.
A) isothermic.
B) endothermic.
C) quasithermic.
D) exothermic.
18) Equilibrium is reached in a chemical reaction when
A) The forward and reverse reactions stop
B) The reactants are completely consumed
C) The rates of the opposing reactions become equal
D) The concentrations of all reactants and products become equal
18)
19) The addition of a catalyst to a chemical reaction would change the
A) Temperature of the reaction
B) Concentration(s) of the product(s)
C) Concentration(s) of the reactant(s)
D) Activation energy
19)
20) In which direction will the point of equilibrium shift when the temperature is increased in the
following equilibrium? N2 (g) + 3 H2 (g) ⇌ 2 NH3 (g) + heat
A) Shift to the right
B) No shift
C) Shift to the left
20)
21) In which direction will the point of equilibrium shift when the volume is increased in the following
equilibrium? heat + N2 O4 (g) ⇌ 2 NO2 (g)
A) Shift to the right
B) No shift
C) Shift to the left
21)
3
22) Which of the following ways would the point of equilibrium shift toward to left (reactant) in the
following equilibrium? N2 (g) + 3 H2 (g) ⇌ 2 NH3 (g) + heat
A) Lower the temperature of the reaction.
B) Increase the concentrations of N2 (g) and/or H2 (g) or both
C) Reduce the concentrations of NH3 (g)
D) Increase the pressure of the system.
22)
PROBLEMS. Show work with proper Significant Figures and Units to receive credit. 10 pts for each question unless
otherwise noted.
23) (6 pts) Name the following compounds:
BrF7
bromine heptofluoride
As2 S4
diarsenic tetrosulfide
24) (6 pts) Write formula for the following compounds:
dinitrogen pentoxide
N2O5
tetraphosphorus hexoxide
P4O6
25) (28 pts) Write Lewis structures AND find the bond angles for the following :
CO 3 2-
HCN
120
Bond angle: <O-C-O = <H-C-N =
H2 CO
180
CHF3
120
Bond angle: <H-C-O = <H-C-F =
4
109.5
26) (15 pts) Balance the following chemical equations:
10
9
2
4
8
____ C
2H5NO2 + ____ O2 → ____ CO2 + ____ H2O + ____ N2
8
8
2
1 4H8O + ____ O
11 2 → ____CO
____ C
2 + ____H2O
3
2
1
9
____ K
2SO4 + ____ Th(NO
3)3 → ____ Th2(SO4)3 + ____ KNO3 27) A. Calculate the molar mass of Pb(N3 )2 .
molar mass = 291.26 g/mol
B. How many moles of the above compound are in 1.00 g Pb(N3 )2 ?
mol = mass/molar mass = 0.00343 mol
28) A. How many gold atoms are present in 0.400 mole of Au?
#atoms = mol x 6.022E+23 atom/mol = 2.41E+23 atoms
B. How many moles of gold are for 9.03 × 1023 gold atoms?
mol = 9.03E+23/6.022E+23 = 1.50 mol
5
29) (15 pts) Anti-acid tablets (such as Rolaid) neutralizes the excess HCl in gastric juice:
2HCl + CaCO3 → CaCl2 + CO2 + H2 O
Based on the above equation, how many grams of HCl will be consumed by 1.50 g CaCO 3 ?
30) (4 pts) Write the equilibrium constant expression for 2 NO2 (g) + 7 H2 (g) ⇌ 2 NH3 (g) + 4H2 O(g)
6
Answer Key
Testname: 2A_S15_T2
1) D
2) D
3) C
4) C
5) C
6) D
7) C
8) D
9) B
10) B
11) C
12) B
13) C
14) C
15) C
16) B
17) B
18) C
19) D
20) C
21) A
22) C
23)
24)
25)
26)
27) 291.26 amu
28) 2.40 × 1023
29) 1.00 g CaCO3 x 1 mol/100.09 g x 2 mol HCl/1 mol CaCO3 x 36.46 g HCl/mol
= 0.729 g HCl
[NH3 ]2 [H2 O] 4
30) Keq = [NO2 ]2 [H2 ]7
7