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Kingdom of Saudi Arabia
King Saud University
College of Science- chemistry Department
CHEM 105 ( General Chemistry for Health Sciences)
Second Semester – 2 Mid Exam. 1427-1428
Serial No. :
Student,s name :
Student,s number:
Choose the correct answer :1- An endothermic reaction is one in which there is
a. a positive value for the work (w > 0 joules
b. a negative value for ΔH (ΔH < 0 joules)
c. a positive value for ΔH (ΔH > 0 joules)
d. a negative value for ΔE (ΔE > 0 joules)
2- For a change in a system taking place at constant pressure, which statement below is
true?
a. ΔH = ΔE
b. ΔH = qp - P ΔV
c. ΔH = ΔE - qp
d. ΔH = qp
3- Using these bond enthalpies, ΔHo:
CC: 348 kJ
CH: 412 kJ
C═C: 612 kJ
HH: 436 kJ
C≡C: 960 kJ
The value of ΔHo of the following reaction is:
H2C═CH2(g) + H2(g) → CH3CH3(g)
a.
b.
c.
d.
-560 kJ
-124 kJ
-388 kJ
+224 kJ
4- if the standard enthalpy of reaction, Ho for
C2H2(g) + 2 H2(g)  C2H6(g)
-1
is -311.5 kJ mol . Determine the value of Eo for this reaction.
a.
b.
c.
d.
-306.5 kJ mol-1
-309.0 kJ mol-1
-314.0 kJ mol-1
-316.46 kJ mol-1
5-Introduction of 430 J of heat caused the system to expand, doing 238 J of work, What
is the value of ΔE for this process?
a.
b.
c.
d.
(430 + 238) joules
(430 - 238) joules
(238 - 430) joules
430 joules
6- which of the following statements is correct?
a. quantity of heat (q) is a state function
b.Enthalpy of formation is always endothermic
c. Δ H is always greater than ΔE
d. Δ H of dissociating of a molecule into constituent atoms called Δ Hatom.
7- The thermochemical equation which is associated with H of , the standard enthalpy of
formation, for HCl(g), is
a.
b.
c.
d.
H(g) + Cl(g) → HCl(g)
H2(g) + Cl2(g) → 2 HCl(g)
½ H2(g) + ½ Cl2(g) → HCl(g)
H2(g) + Cl2(l) → 2 HCl(g)
8- The volume of ballon changes from14ℓ to 20ℓ by the addition of 2027 J of heat .If the
ballon expand against aconstant preasure of 10 atm. Calculate Δ E for this process
in joule ( 1ℓ atm = 101.35 J )
a. 4054
b. 6081
c. -6081
d. -16216
9- For asystem , if Ef > Ein :
a. energy transfere from asystem to surrounding
b. energy transfere from asurrounding to system
c. no change in energy
d. no correct answer
10-By using these thermochemical equations :
C2H2 (g)
+ 5/2 O2 (g)
→
2CO2 (g)
+ H2 O (g)
What is ∆ H°f for C2H2 (g) ( in Kcal ) knowing that :
∆ H°f CO2 (g) = - 68.3 Kcal and ∆ H°f H2 O (g) = - 92.2 Kcal
∆ H° = - 30 Kcal
b. – 541.5
a. 148.2
c. 79.9
d. - 85.6
11-When B. E . has apositive value :
a. bond broken and energy released
b. bond broken and energy absorbed
c. bond formed and energy released
d. bond formed and energy absorbed
12-From the f ollowing dada :
H2 (g)
+ Cℓ2 (g)
∆ H° = -185 Kj
→ 2H Cℓ (g)
∆ H° = - 483 kj
2H2 (g) + O2 (g) → 2H2O (g)
∆ H° for the reaction (in Kj) :
4 HCℓ (g)
a. -113
+ O2 (g) →
2 Cℓ2 (g) + 2H2 O (g) is :
b. -298
c.-668
d. 256
13-Given the following data :
N2H4 (ℓ) + O2 ( g)
)
→
∆ H° = - 622.4 Kj
N2 (g) + 2 H2O (ℓ)
What quantity of heat ( in Kj ) is liberated by the combustion of 100g of N2H4
a.34.5
b. 199.2
c. 6.5
d. 1945
14-Caculate the energy of C = C in H—C = C---H ( in Kj / mol ) if :
2C (s) + H2 (g ) → C2 H2 (g )
∆ H°f H = 218 Kj / mol ,
415 Kj / mol
a. 833
b. 830
∆ H°f C = 715 Kj / mol and C—H bond energy =
c. 840
15- Calculate ∆ H°atm of C6 H6
∆ H°f C2H2 = 203 Kj ,
d. 844
knowing that the bond energy of C—H
,C—C , C = C ( in Kj / mol ) are :
415
, 343 , 607, respectively .
Answer is :
16. Using the following data:
o
Cs (s) + 1/2Cl2 (g)  CsCl (s)
∆Hf CsCl (s) = -443 kJ/mol
∆Hsubl. Cs (s) = +78 kJ/mol, ∆Hion. en, Cs (g) = +375 kJ/mol,
∆Hdiss. en. Cl2 (g) = +243 kJ/mol and ∆Helec. aff. Cl (g) = -349 kJ/mol,
The Lattice energy of CsCl (s) (in kJ/mol) is:
a) -320
b) -591
c) -669
d) -112
17. Which of the following does not obey Octet rule?
a) H2S
b) IF5
c) PBr3
d) CBr4
18. The correct Lewis structure for the molecule H2CO is:
..
..
:O:
.. ..
O:
a) H – C – H
b) H – C – O – H
c) H – C – H
..
..
..
..
.. .. H
d) :C – O
..
H
o
19. To calculate ∆Hf for the K2O using Born-Haber cycle, we need:
a)
b)
c)
d)
The 1st and 2nd ionization energy for potassium
Double the electron affinity for oxygen
Double the 1st ionization energy for potassium
Ionization energy and electron affinity are not needed for the calculation
20. The bond energy will be increased by:
1) Increasing bond order
3) Increasing vibrational frequency
a) 2,3
b) 2.4
2) Increasing bond length
4) Decreasing vibrational frequency
c) 1,3
d) 1,2
21. In which compound have electrons been transferred to the oxygen atom?
a) CO2
b) NO2
c) N2O
d) Na2O
22. Which of the following is an electron deficient compound?
a) NH3
23.
b) CH4
. .
. N:
.
b) Fewer protons
c) More electrons
d) Fewer electrons
Intermolecular attractive forces of the Dipole-Dipole type exist in:
a) CCl4
26.
.
..
d)
A Mg2+ ion differs from Mg atom in that the Mg2+ ion has:
a) More protons
25.
d) SF4
The correct Lewis symbol for the atom of nitrogen is:
.
.
..
a) . N .
b) . N:
c)
:N:
.
24.
c) BCl3
b) Ar
c) Cl2
d) H2S
Which statement is incorrect?
a) London forces are present in all substances
b) London forces are stronger in Cl2 than in I2
c) Dipole-Dipole forces exist in SO2 but not in CO2
d) The total strength of the London forces are larger in C6H18 than in C3H8
___________________________________________________________________
27.
In which of the following substances does hydrogen bonding exist?
a) PH3
28.
d) CH2Br2
b) BiH3
c) PH3
d) AsH3
Which of the following has both London forces and Dipole-Dipole interaction?
a) CH4
30.
c) CH3COCH3
Which of the following compounds has the highest vapor pressure?
a) SbH3
29.
b) HOOH
b) XeF4
c) HCl
d) Ne
Which of the following liquids has the highest heat of vaporization?
a) Kr
b) Ne
c) He
d) Xe
31. The weaker the intermolecular attraction forces the higher is (or are):
1) heat of vaporization
3) distance between molecules
a) 1,2
b) 2,4
2) vapor pressure
4) boiling point
c) only 3
d) 2,3
Choose the correct answer :1-A chemical reaction took place in a cylindrical fitted with a piston .a volume change
from 0.400 liters to 3.20 liters. Which statement below is true :
a.
b.
c.
d.
Work was don on the system.
Work was don by the system.
The internal energy of the system increased.
The internal energy of the system decreased.
2-The mathematical equation below which expresses the first law of thermodynamics is
a.
b.
c.
d.
H
H
H
E
= E + pV
= E - pV
=q + w
=q + w
3- For a chemical reaction taking place at constant volum in which all reactants and
products are solids or liquids, ΔE ≈ .
a. q p
b. qv
c. PV
d . nRT