Supplemental Instruction
Iowa State University
Leader: Grant DeRocher
Course: Chem 167
Instructor: Houk
Date: 05/5/13
1.
How many significant numbers are in the these measured quantities?
(a) 1374 kg 4
(b) 0.00348 s
(c) 5.619 mm
(d) 2.475 x 10
-3
cm
3
4
4
Pg 16
2.
Accuracy vs precision
Accuracy indicates how close the observed value is to the true value.
Precision is the spread in values obtained from the measurement.
3.
How many protons, neutrons and electrons does
40
K
3+
have?
21 neutrons since 40 is the mass minus 19 for the number of protons of K.
Has 3+ charge to 3 more protons than electrons so 16 electrons.
4.
Given the following chart, calculate the atomic mass of Uranium.
Isotope
35
Cl
37
Cl
Abundance
75.77%
24.23%
Mass
34.97 amu
36.95 amu
.7577*34.97 + .24*24.23 = 35.45 amu
5.
Name each of the following compounds: (a) MgCl
2
(b) N
2
O
5
(a) Magnesium chloride, covalent compound
(b) Dinitrogen Pentoxide, ionic compound
6.
Balance this equation: Fe(s) + H
2
O(g)
What is the balanced coefficient for H
2
O?
3Fe(s) + 4H
2
O(g) Fe
3
O
4
(s) + 4H
2
(g)
Fe
3
O
4
(s) + H
2
(g)
7.
How many moles are in 67.56 g of Ni?
67.56g*(1mol/58.69g) = 1.151 mol
8.
A compound has empirical formula H
2
SO
4
and molar mass 394.27 g/mol. What is its molecular formula?
1.01*2+32.07*1+16.00*4=98.09 394.27/98.09=3 so H
6
S
3
O
12
8. If 522.82 g of disiline, Si
2
H
6
, is combined with 483.2 g O
2
, which is the limiting reagent?
Si
2
H
6
+ O
2

SiO
2
+ H
2
O NOT BALANCED

Pick one reactant. Doesn’t matter which one and calculate how much of the other reactant is required for a complete reaction. Then compare that number with how much we actually have in order to see which one is the limiting reactant.
Convert to moles. 8.4 moles Si
2
H
6
. 15.1 mol O
2
8.4*(7 mol O/ 2 mol Si
2
H
6
)= 29.4 moles O
2
required to react with all the Si
2
H
6
. Since more O
2
is required than what we have, O
2
is the limiting reactant.
9.
If 2.70 mL of 12.0M NaOH is diluted to a volume of 150.0 mL, what is the final concentration?
M i
= 12.0 V i
= 2.70 mL M f =
x V f
= 150.0 mL 12*2.7= x*150 x = .216M
10.
A sample of CO
2
gas has a pressure of 56.5 mm Hg in a 125 mL flask. The sample is transferred to a new flask where it has a pressure of 62.3 mm Hg at the same temperature. What is the volume of the new flask?
PV=nRT R is always constant and it tells us T is constant. Also since the sample is transferred, the number of moles is constant. So all we have left is volume and pressure. So we know to use
P1V1=P2V2 . Solve for units first and put values in second. So V2=P1V1/P2 and V2=
56.5*125/62.3=113mL. Units for volume and pressure don’t matter in this formula as long as they are consistent
11.
Methanol, CH
3
OH, is used in racing cars because it is a clean-burning fuel. It can be made by this reaction: CO(g)+ 2H
2
(g) CH
3
OH(l)
What is the percent yield if 5.0x10
23
g H
2
reacts with excess CO to form 3.5x10
3
g
CH
3
OH?
5.0x10
23
g H2*1 mol H2/2.02g H2*1 mol methanol/2 mol H2*32.04g methanol/1 mol methanol= 4.0x10
4 g methanol
Now do percent yield: 3.5x10
3
/4.0x10
4
= 8.8% yield. Not a good yield.
12.
What is the total pressure(in atm) of a 15.0-L container at 28.0 degrees C that contains 3.5g N
2
, 4.5 g O
2
, and 13.0 g Cl
2
?
Same strategy as last time. Just make sure to use atmospheres.
Find mol of each one .125 mol N
2
+.141 mol O
2
+ .183 mol Cl
2
= .449 mol total
T= 301.15 K now use with ideal gas law PV=nRT. Answer= .74 atm
.449*.08206*301.15/15=.74 atm
13.
Write the ground state electron configuration for (a) B (b) Ba (c) Be.
(a) 1s
2
2s
2
2p
1
(b) [Xe] 6s
2
(c) [He] 2s
2

14.
When light with a wavelength of 58.5 nm strikes the surface of tin metal, electrons are ejected with a maximum kinetic energy of 2.69 x 10
-18
J. What is the binding energy of these electrons to the metal?
The binding energy is related to the energy of a photon:
E= Binding E + Kinetic E.
Calculate the energy of the photon with the wavelength and then find the binding energy using the kinetic energy given.
E photon
= hc/λ = (2.626x10
-34
J*s)(3.0x10
8
m/s) / (58.5nm*1x10
-9 m/ 1nm) = 3.40 x 10
-
18
J/photon.
Binding E= 3.40 x 10
-18
J – 2.69x10
-18
J= 7.1x10
-19
J
15.
Arrange the following set of anions in order of increasing atomic radii: (a) Cl
-
, P
3
-
,
S
2
-
(a) Cl-, S2-, P3-
16.
Which of the following represent valid sets of quantum numbers?
(a) n=3, l=3, m l
=0 no f orbitals at n=3 level
(b) n=2, l=1, ml=0 good to go
(c) n=6, l=5, ml= -1 can’t have n=6, only 4 levels
(d) n=4, l=3, ml=-4 ml can’t be -4. 7 values centered around 0.
17.
Arrange the following atoms in order of increasing ionization energy: Li, K, C and
N.
K, Li, C, N
18.
Indicate which species in each pair has the more favorable (more negative) electron affinity. (a) Cl or S (b) S or P
(a) Cl (b) S
19.
Draw the Lewis dot structure of the following species and identify the number of pi bonds in each: (a) CS
2
(b) CH
3
Cl (c) NO
2
-
Pi bonds are found in double or triple bonds. Each double bond has 1 pi bond and each triple bond has two pi bonds.
(a) Two pi bonds
(b) Zero pi bonds
(c) One pi bond
20.
Predict the geometry of the following species: (a) SO
2
(b) BeCl
2
(c) SeCl
4
21.
Predict the shape of each of the following molecules or ions: (a) IF
3
(b) ClO
3
-
(c)
TeF
4

22.
Based on the positions in the periodic table of the following pairs of elements, predict whether bonding between the two would be primarily ionic or covalent. (a) Ca and Cl
(b) Ba and F (c) Br and I
(a) Ionic
(b) Ionic
(c) Covalent
23.
What hybrid orbitals would be expected for the central atom of GeCl
4
?
Sp
3
24.
Identify the kinds of intermolecular forces that are most important in methanol,
CH
3
OH.
A. London dispersion B. H-Bonding C. Covalent bonding D.
Dipole-dipole
25.
Write a formation reaction for C
8
H
10
O.
8C(s) + 5H
2
(g) + 1/2O
2
(g)
26.
What is the symbol for giving off heat?
-q
C
8
H
10
O
27.
For the reaction N
2
(g) + O
2
(g) 2NO(g) ∆H=180.5kJ, how much energy is required to generate 1050.35 grams of NO?
1050.35g NO*(1 mol NO/30.01g NO)*(1 mol rxn/2 mol NO)*180.5 kJ= 3200kJ
28.
How fast (in meters per second) must an iron ball with a mass of 56.6 g be traveling in order to have a kinetic energy of 15.75 J? The density of iron is 7.87 g/cm
3
.
KE= ½ mv 2
15.75 = .5*(56.6)*v
2
v=.746 m/s
29.
The first order rate constant for the photodissociation of A2 is 0.231 s-1. How much time is needed for the concentration of A2 to decrease to one-fifth (20%) of its initial concentration?
A) 10.3 s B) 6.97 s C) 3.45 s D) 0.179 s
[A t
]=[A
0
]e
-kt
.2= e
-.231t
ln(.2)=-.231t t=6.97 seconds
30.
A metal radiator is made from 26.0 kg of iron. The specific heat of iron is 0.449
J/g*degreesC. How much heat must be supplied to the radiator to raise its temperature from 25 degrees C to 55 degrees C?
Heat flow can be calculated by q= mc∆T. m=26.0kg=26000g c=.449J/g*degreesC ∆T=30 degrees C q=(26000)(.449)(30)= 3.5x10
5 J
31.
For the reaction 2NO(g) + 2H
2
(g) N
2
(g) + 2H
2
O(l)
AT 1100 degrees C, the following data have been obtained.

[NO](mol L
-1
)
5.0x10
-3
1.0x10
-2
1.0x10
-2
[H
2
](mol L
-1
0.32
0.32
0.64
) Rate=-[NO]/∆t (mol L
-1
0.012
0.024
0.096
s
-1
Describe the rate law for the reaction, and determine the value of the rate constant.
The rate law is: rate= k[NO] x
[H
2
] y
Comparing experiment 1 to experiment 2, the [H
2
] stays constant and the [NO] doubles.
The rate also doubles. This implies x=1.
Mathematically, using the rate law: 2(rate)=[2NO] x , 2=2 x , x=1
Next, compare experiment 2 to experiment 3. The [NO] stays constant and the [H
2
] doubles. The rate quadruples. This implies y=2.
Mathematically using the rate law: 4 rate= [2H
2
] y
4=2 y
y=2
The rate law now becomes: rate=k[NO]
1
[H
2
]
2
To finish, plug ANY experiment in and solve for k. Using the first one:
0.012 Ms
-1
= k [0.0050M][0.32M]
2
Solving, rate= 23M -2 s -1 [NO][H
2
]
)
32.
HBr is oxidized in the following reaction:
4HBr(g) + O
2
(g) 2H
2
O(g) + 2Br
2
(g)
A proposed mechanism is
HBr + O
2
HOOBr
HOOBr + HBr 2HOBr
(slow)
(fast)
HOBr + HBr H
2
O + Br
2
(fast)
(a) Identify all intermediates in this mechanism
(b) Identify the rate determining step
33.
The following reaction is at equilibrium:
HF(g) + H
2
O(l) H
3
O
+
(aq) + F
-
(aq)
If water is added to the system, what will happen?
A. [F
-
] will increase B. [H
3
O
+
] will decrease C. [HF] will decrease
D. Concentrations will not change
We won’t have time to cover everything from chapters 13 and 14 but since those are the most recent chapters they should be more fresh in your mind. Refer to www.si.iastate.edu
and go to Chem 167 to find my SI worksheets over these chapters.

Sessions 33 and after. I will post the solutions to these lessons on the website but you need to try them on your own first or you won’t be doing yourself any favors. Go through the chapters since the last test and make sure you have the new equations that will be important on your periodic table. This is the last time you will need it to don’t hold back. Fill up all of your space. But make sure you can find it come test time.