Download Exam 1 Review

Chemistry 140
Exam #1
Fall 2009
The first exam for this course will be given in class on Friday, September 18, and will cover material in
Chapters 7 – 10 of the textbook.
The following sections will be covered on the exam:
7.4 7.7, 7.9 9.3
8.1 – 8.11, 8.13-8.14
10.1 – 10.5, 10.11
skip dipole moment calculation (in 10.2), Claussius-Clapeyron equation (in 10.5)
It is particularly important to study and do the problems for the following sections:
7.9
8.4
8.5
8.8
8.14
10.2
10.4
Questions that may appear on the exam:
Calculate ΔH using: Hess’s Law, heats of formation, bond dissociation energies
Given ΔH for a reaction, how much heat is released when 20 g of product is formed?
(hint – use the balanced chemical equation to solve)
Find heat needed to change water at 20 °C to steam at 100 °C.
Does entropy increase or decrease for a given reaction?
When is a reaction spontaneous? Is positive or negative entropy more favorable?
What do exothermic and endothermic mean?
What does ΔG = 0 mean?
What is a London dispersion force? How strong is it compared to other forces?
Which compound has the highest boiling point? Which can undergo hydrogen bonding?
What is the definition of boiling point?
What is the triple point? What does supercritical mean?
Topics that will likely be on the test:
Changing moles to grams, grams to moles
ideal gas law
Hess’s Law and ΔH calculations
electronegativity
State functions
covalent bonds – polar and non-polar
PV work
entropy (ΔS) and enthalpy (ΔH)
free energy (ΔG) and spontaneous reactions
bond dissociation energies
electron pair geometry (look at atoms AND lone pairs around a central atom)
molecular shape (consider only atoms around a central atom)
phase diagram: triple point, supercritical fluid
phase changes: fusion, vaporization, sublimation, condensation, freezing, deposition
intermolecular forces: dipole-dipole, hydrogen bonding, London dispersion force
Calculations that may be required:
w = -PΔV
expansion work
q = m c ΔT
gives q (in J) for heating (remember m is mass in grams)
q = (moles) x ΔHfusion
gives q (in kJ) for phase change (remember to covert to moles)
q = (moles) x ΔHvap
gives q (in kJ) for phase change (remember to covert to moles)
ΔHrxn = ΔH°formation(products) – ΔH°formation(reactants)
ΔHrxn = Sum of Dbonds broken – Sum of Dbonds formed
(D – bond dissociation energy)
ΔG = ΔH – T ΔS
PV = nRT
Calculating molar mass and converting between grams and moles
Chem 140
Exam 1 Practice Problems
1. According to the ideal gas law, a 98.1-gram sample of nitrogen gas (N2) at 2 atm and 0 °C would
have a volume of:
a. 3.75 L
b. 4.78 L
c. 25.34 L
d. 39.2 L
e. 3.59 L
2. The mass of 1.24 moles of barium hydroxide Ba(OH)2 will be
a. 191.3 g
b. 212.4 g
c. 55.6 g
d. 138.2 g
3. Hydrogen bonding can take place in which of the following substances?
a. CH3CH2-Br
b. N(CH3)3
c. HO-CH2CH2-OH
d. NaH
e. 192.6 g
e. CH3OCH2SH
4. Rank the three compounds shown in order of increasing boiling point.
I. CH3CH2CH2Cl
II. CH3CH2CH2F
III. CH3CH2CH2OH
5. For which reaction below is there the greatest increase in entropy?
a. CH2O (l) + H2O (l)
→
CH4O2 (l)
b. 2 Na (s) + Cl2 (g)
→
2 NaCl (s)
c. CaCO3 (s)
→
CaO (s) + CO2 (g)
6. The intermolecular force based on attraction of temporary dipoles in neighboring molecules is:
a. a dipole-dipole force b. hydrogen bonding c. London dispersion forces d. ionic attraction
7. The place on a phase diagram where solid and liquid are in equilibrium is called
a. the triple point
b. the normal melting point
c. the solid-liquid boundary
d. the supercritical fluid
8. A chemical reaction taking place at 24 atm of pressure results in the volume of the system
decreasing from 140 L down to 110 L. What was the change in work for the gas in this reaction?
a. +720 L·atm
b. -1250 L·atm c. +2.64 L·atm d. -3360 L·atm e. +1389 L·atm
Problems:
Work out answers to the following problems. Work must be shown for calculations.
9. Given the following data:
S (s) + O2 (g)
2 SO3 (g)
SO2 (g)
2 SO2 (g) + O2 (g)
∆H° = -296 kJ
∆H° = +198 kJ
Use Hess’s Law to calculate ∆H° for the reaction shown below:
2 S (s) + 3 O2 (g)
2 SO3 (g)
∆H° = ?? kJ
10. Using the balanced chemical equation below, calculate the amount of heat evolved or absorbed when
27.5 g of potassium reacts with water to form KOH and H2 gas.
2 K (s) + 2 H2O (l)
11.
2 KOH (aq)
+
H2(g)
ΔH° = -394.1 kJ
Use data from the front page of this exam to find the total heat (q) needed to convert 120 g of ice,
H2O (s), at –10 °C to H2O (l) at +50 °C.
Chemistry 140
Exam #1
Fall 2009
September 18, 2009
Name:
INSTRUCTIONS:
Prefix
gigamegakilodecicentimillimicronano-
In order to receive full credit, all work must be CLEARLY shown.
Partial credit may be awarded if work is shown.
Exam is closed book and closed notes.
Use the scratch paper at the end of the exam (do not use your own paper).
Symbol
G
M
k
basic unit
d
c
m
μ
N
Multiple/Fraction
1 X 109
1 X 106
1 X 103
1
1X 10-1
1X 10-2
1 X 10-3
1X 10-6
1 X 10-9
1 in. = 2.54 cm
1 lb = 454 g
1 min = 60 sec
1 hr = 60 min
1 ml = 1 cm3
π = 3.14
D = mass/vol
1 mole = 6.02 X 1023
Vol(rectangular solid)= l x w x h
PV = nRT
1 atm = 760 mm Hg
TºC +273 = TK
molar volume of gas at STP = 22.4 L
STP = 1 atm and 0 ºC
• atm
R = 0.0821 Lmol
•K
ΔE = q + w
w = –P ΔV
ΔG = ΔH – T ΔS
q = moles (ΔHvap)
q = m c ΔT
101 joules = 1 L·atm
1 kcal = 4.184 kJ
Specific Heat
Substance
water (liq)
water (s)
ammonia (NH3)
ethanol (C2H6O)
mercury (Hg)
iron (Fe)
copper (Cu)
(J/g·C˚)
4.18
2.03
2.46
0.140
0.349
0.385
1 mm Hg = 1 torr
Molar
Heat Capacity
Heat of Fusion
Heat of Vap
(J/mol·C˚)
(ΔHfusion, kJ/mol)
(ΔHvap, kJ/mol)
75.3
36.6
28.0
25.1
24.4
6.01
6.01
5.97
5.02
2.33
3.21
4.05
40.7
23.4
38.6
56.9
65.0