AP Chem
1.
Test 5-7 Practice Exam Answer Key (41 points)
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Use the following balanced chemical reaction to answer the following questions: (5 points)
C2H4 (g) + ICl5 (g) → 2 CH2Cl2 (g) + ICl (g)
Given:
ΔHfº (kJ/mol)
ICl5 (g)
- 472.5
ΔHf C2H4 = 52.26 kJ/mol
CH2Cl2 (g)
- 403.4
ICl (g)
135.0
C2H4 (g)
52.3
Calculate ΔHrxn for this reaction using the standard molar heats of formation. -251.56 kJ/mol
First
Ionization Energy
(kJ mol-1)
Second
Ionization Energy
(kJ mol-1)
Third
Ionization Energy
(kJ mol-1)
Element 1
1,251
2,300
3,820
Element 2
496
4,560
6,910
Element 3
738
1,450
7,730
Element 4
1,000
2,250
3,360
2. The table above shows the first three ionization energies for atoms of four elements from the third
period of the periodic table. The elements are numbered randomly. Use the information in the table to
answer the following questions. (each part is one point)
(a)
Which element is most metallic in character? Explain your reasoning. Element 2, lower IE
(b)
Identify element 3. Explain your reasoning.Mg, high jump in IE between second and third, 2
valence electrons
(c)
Write the complete electron configuration for an atom of element 3. 1s22s22p63s2
(d)
What is the expected oxidation state for the most common ion of element 2? 1+
(e)
What is the chemical symbol for element 2? 2311 Na
(f)
A neutral atom of which of the four elements has the smallest radius.element 1, larger IE
(a)
(b)
(c)
(d)
(e)
(f)
3. Name the element corresponding to each characteristic below.(each part is one point)
the element with the electron configuration 1s22s22p63s23p3 P
the alkaline earth element with the smallest atomic radius Be
the element with the largest ionization energy in Group 5A N
the element whose 2+ ion has the configuration [Kr] 4d5 Tc
the element with the most negative electron affinity in Group 7A F
the element whose electron configuration is [Ar]3d104s2 Zn
4. It takes 254 kJ/mol to eject electrons from a certain metal surface. What is the longest wavelength of
light (nm) that can be used to eject electrons from the surface of this metal via the photoelectric effect?
(5 points)
E=254 kJ/mol
E=4.22 x 10-22 kJ/photon
E= hc/λ → λ=hc/E=(6.626 x 10-34 j.s.x 3 x 108 m/s)/(4.22 x 10-22j)
= 4.71 x 10-7 m
= 471 nm
Multiple Choice Questions: (each question is worth 2 points)
1. The value of ∆H0 for the reaction below is -126 kJ. The amount of heat that is released by the reaction of
25.0 g of Na2O2 with water is __________ kJ.
2 Na2O2 (s) + 2 H2O(l)  4 NaOH(s) + O2(g)
A) 20.2
2(46g + 32g) = 156g Na2O2
156 g Na2O2
→ -126 kJ
25.0 g Na2O2 → -20.2 kJ
B) 40.4
C) 67.5
D) 80.8
E) -126
2. The ΔH for the exothermic solution process when solid sodium hydroxide dissolves in water is 44.4 kJ/mol.
When a 13.9-g sample of NaOH dissolves in 250.0 g of water in a coffee-cup calorimeter, the temperature
change is _______. Assume that the solution has the same specific heat as liquid water, i.e., 4.18 J/g-K.
3.
A) 35.2 °C
B) 13.8 °C
qrxn + qsoln = 0
qrxn + (13.9 +250)g x 4.18J/g°C x ∆T=0
1 mol=44.4 kJ
40g→44 kJ
C) 37.8 °C
(-15290 J) + (1103.10) ∆T = 0
13.9g → 15.29 kJ
D) 37.0 °C
E) 40.2 °C
∆T= +13.8 °C
Given the following reactions
(Fe2O3(s) + 3 CO(g) 2 Fe(s) + 3CO2(g) ΔH = -28.0 kJ) x 3
(3Fe(s) + 4 CO2(g) 4CO(g) + Fe3O4(s) ΔH = +12.5 kJ) x 2
the enthalpy of the reaction of Fe2O3 with CO
3 Fe2O3(s) + CO(g)  CO2(g) + 2 Fe3O4(s) is __________ kJ.
A) -59.0
B) 40.5
C) -15.5
D) -109
E) +109
+
3Fe2O3(s) + 9 CO(g) 6 Fe(s) + 9CO2(g)
6Fe(s) + 8 CO2(g) 8CO(g) + 2Fe3O4(s)
3Fe2O3(s) + CO Fe3O4
ΔH=-84kJ
+ ΔH=25kJ
ΔH=-59kJ
4. A tin atom has 50 electrons. Electrons in the __________ subshell experience the lowest effective nuclear
charge.
A) 1s
B) 3p
C) 3d
D) 5s
E) 5p
5. Element M reacts with chlorine to form a compound with the formula
. Element M is more reactive
than magnesium and has a smaller radius than barium. This element is __________.
A) Sr
B) K
C) Na
D) Ra
E) Be
6. Of the following, which gives the correct order for atomic radius for Mg, Na, P, Si and Ar?
A) Mg > Na > P > Si > Ar
B) Ar > Si > P > Na > Mg
C) Si > P > Ar > Na > Mg
D) Na > Mg > Si > P > Ar
E) Ar > P > Si > Mg > Na
7. The electron configuration of the phosphide ion (P3-) is __________.
A)[Ne] 3s2
B) [Ne] 3s23p1
C) [Ne] 3s23p3
D) [Ne]3p2
E) [Ne] 3s23p6
Lab Question
A student tried to find the heat produced per g of Cheetos using the Calorimetry lab and got the following data:
(5points)
Food Sample
Mass
before
burning (g)
Mass after
burning (g)
Initial
Temperature
(°C)
Final
Temperature
(°C)
Mass of
Water +
Beaker
Mass of
Beaker
Hot Cheetos
1.00 g
0.570 g
25.00
25.35
110 g
70.0 g
How many calories are produced by burning 1.0 g of Cheetos?(hint: specific heat of water in calories is: 1.0
cal/g°C)
q=mc∆T
mass of water: (110-70)g = 40g
c of water= 1.0 cal/g°C
∆T= (25.35-25.00)°C= 0.35°C
q= 40 x 1.0 x 0.35= 14 cal
mass of food burned: (1.00-0.570)g = 0.430g
calories produced: 14cal / 0.430g = 32.6 cal/g Cheetos