CH 5, 7, 8, 9 Assessment 2009-2010
1. Answer the following using chemical concepts and principals of the behavior of gases.
(a) A metal cylinder with a volume of 5.25 L contains 3.22 g of He(g) and 11.56 g of N 2 (g) at 15.0°C.
(i) Calculate the total pressure in the cylinder.
(ii) Calculate the partial pressure of N2 in the cylinder.
(b) A 1.50 L container holds a 9.62 g sample of an unknown gaseous saturated hydrocarbon at 30.0°C
and 3.62 atm.
(i)
(ii)
(iii)
(iv)
Calculate the density of the gas.
Calculate the molar mass of the gas.
Write the formula of the hydrocarbon.
Calculate the root mean square velocity of the gas molecules in the container at 30.0°C.
**Note 1 J = 1 kg · m2 s-2
2. Answer each of the following using principles of atomic or molecular structure.
(a) Explain why the H—O—H bond angle in H2O is less than the H—N—H bond angles in NH3.
(b) Explain why the radius of the Br atom is less than the radius of the Br 1- ion.
(c) Explain why the dipole moment of HI is less than the dipole moment of HCl.
3. Answer the following questions related to sulfur.
(a) Consider the atom sulfur, and its ion, sulfide.
(i) Draw the orbital diagram for the atom AND the ion.
(b) Name the atom that is isoelectronic with the sulfide ion.
(i) Would it be easier to remove an electron from the sulfide ion, or from the isoelectronic
atom? Explain.
4. Draw complete Lewis Dot Diagrams for the molecules CH4, PF5 and SF4. Identify the bond angle,
hybridization of the central atom and geometric (VSEPR) shape of each molecule.
5. There are two Lewis structures possible for the molecule OPF3. In one structure there are 4 sigma bonds on
the central phosphorus atom, and on the other, there are 4 sigma bonds and one pi bond. Which structure
would best represent this molecule? Justify your answer in terms of formal charge.
Directions: Each set of lettered choices below refers to the numbered statements immediately following it. Select the
one that is best in each case and then place the letter of your choice on your answer sheet. A choice may be used more
than once, or not at all in each set.
Questions 1-3 refer to the following molecules.
(A)
(B)
(C)
(D)
(E)
1.
2.
3.
CO
CH4
HF
PH3
F2
Contains two π-bonds
Has the highest dipole moment
Has the molecular geometry that is trigonal pyramidal.
Questions 4 through 7 refer to neutral atoms with the following electron configurations.
(A)
(B)
(C)
(D)
(E)
4.
5.
6.
7.
1s2
1s22s12p1
1s22s22p3
1s22s22p6
[Ar]4s23d8
Is in an excited state.
Has exactly five valence electrons.
Has the highest first ionization energy.
Forms an aqueous cation that has color.
8. Of the following gases, which has the greatest average molecular speed at 298K?
(A)
(B)
(C)
(D)
(E)
Cl2
NO
H2S
HCN
PH3
9. Types of hybridization exhibited by the carbon atoms in a molecule of propyne, CH3CCH, include which of the
following?
I.
sp
II.
sp2
III.
sp3
(A)
(B)
(C)
(D)
(E)
I only
III only
I and III only
II and III only
I, II and III
10. In which of the following are the chemical species correctly ordered from the smallest to the largest radius?
(A) B < C < N
(B) Ar < Xe <Kr
(C) Cl < S < S2(D) Na < Na+ < K
(E) K+ < Ca2+ < K
8H2(g) + S8(s)  8H2S(g)
11. When 25.6 g of S8(s) (molar mass of 256 g/mol) reacts completely with excess H2 (g) according to the equation
above, the volume of H2S(g), measured at 0.0°C and 1.00 atm, produced is closest to
(A) 30L
(B) 20L
(C) 10L
(D) 5L
(E) 2L
CS2(l) + 3O2(g)  CO2(g) + 2SO2(g)
12. When 0.60 mol of CS2(l) reacts as completely as possible with 1.5 mol of O2(g) according to the equation above,
the total number of moles of reaction products is
(A) 2.4 mol
(B) 2.1 mol
(C) 1.8 mol
(D) 1.5 mol
(E) 0.75 mol
13. At approximately what temperature will 40.0 g of argon gas at 2.0 atm occupy a volume of 22.4 L?
(A) 1,200 K
(B) 600 K
(C) 550 K
(D) 270 K
(E) 140 K
14. At which of the following temperatures and pressures would a real gas be most likely to deviate from ideal
behavior?
(A) 100 K and 50 atm
(B) 200 K and 5 atm
(C) 300 K and 0.01 atm
(D) 500 K and 0.01 atm
(E) 500 K and 1 atm
Ionization Energy (kJ/mol)
1st
2nd
3rd
4th
5th
6th
7th
787
3200
4400
16000
20000
24000
1580
15. The first seven ionization energies of element X are shown in the table above. On the basis of these data,
element X is most likely a member of which of the following groups (families) of elements?
(A) Alkaline earth metals
(B) Boron group
(C) Carbon group
(D) Nitrogen group
(E) Halogen group