Chem.121 final, Version A

Name:

Student I.D.

  1. The solid fuel in the booster stage of the space shuttle is a mixture of ammonium perchlorate and aluminumpowder, which react as follows: (4 marks)

NH4ClO4(s) + Al(s) → Al2O3(s) + N2(g) + HCl(g) + H2O(g)

a)Balance the equation.

b)What mass of aluminum should be mixed with 5.0 × 103 kg of ammonium perchlorate?

2. The Haber Process for the production of ammonia is represented by: (4 marks)

3 H2(g) + N2(g) → 2 NH3(g)

If a mixture of 30 g of hydrogen with 10 g of nitrogen produced 8.4 g of ammonia, what was the percent yield?

3. A mixture of gases consists of 1.639 × 10-2 mol of Argon (Ar) and 0.8771 mol of carbon dioxide (CO2) contained in a volume of 3.00 L at 37.0°C. What is the total pressure in the container and the partial pressure of each gas?( 3 marks)

  1. Ionization energy (IE) increases from left to right on the periodic table and is a measure of the energy required toabstract an electron. Yet the first IE for phosphorus, P, is larger (10.5 volts) than the first IE of sulfur, S, (10.4 volts). Explain this anomaly. ( 3 marks)
  1. A hydrogen electron makes a transition directly from n = 5 to n = 2. ( 4 marks)

a)Is energy absorbed or transmitted during the transition?

b) Calculate the wavelength of the energy absorbed or transmitted.

  1. Write an orbital diagram for the ground state electron configuration of Fe 2+ andFe 3+?

Using the orbital diagrams, explain why Fe 2+ is easily oxidized toFe 3+?( 3 marks)

  1. Complete the table below. Use shape and electronegativity values. Take the Pauling electronegativity value for Xe = 2.6 and a lone pair = 3.7. (8 marks).

Molecular
Formula / Lewis Structure / Electron Group Geometry
(VSEPR shape)
and
Bond angle / Molecular Geometry name / Hybridization of
Central atom / Overall polarity
(polar or non-polar)
NO3-
BrF3
XeF4
SF6
  1. What is the complete (include cis or trans) systematic name (IUPAC name) for the following molecule? (2 marks)
  1. Draw skeletal isomers ofC3H8O. ( 3 marks)
  1. Arrange the following compounds in order of increasing boiling point. Describe the intermolecular forces between molecules for each compound; give an estimate of the strength of these forces and your reasons for placing the molecule in order with respect to the others.

( 4 marks)

a)CH3CH3, CH3NH2, PH3

b)CH3CH2CH2OH, CH3CH(OH)CH2OH, HOCH2CH(OH)CH2OH.

c)H2S (μ=0.97 D) F2 (μ=0.0 D) HCl (μ=1.11 D) HFO (μ=2.23 D)

d)CBr4, CCl4, CI4, CF4

  1. Draw each of the following compounds: ( 3 marks)

A)cis-1,2-dimethylcyclopropane

B)1,1,1 – trichloroethane

  1. How many primary, secondary, tertiary and quaternary carbon atoms are there in the structure of 2,4,6-trimetylheptane? Draw the structure. (2 marks)
  1. Draw a structure that shows the valence bond orbital overlap for the following:

(4 marks).

a)Methanal (formaldehyde gas) H2CO

b)Ethane, C2H6

  1. Which of the following would have the largest atomic radius? ( 2 marks)

A)Na B) Mg C) Br D) K E) Ca

  1. Draw the molecular orbital energy diagram for N2andC2and determine:

Which species would have: (6 marks)

(i)the weakest bond?

(ii)the shortest bond?

  1. Arrange the following in order of increasing attraction to a magnetic field; Show your work. (4 marks).

Mg

B

As

Cr

  1. This question refers to the phase diagram of carbon dioxide (see below). (6 marks)

a)Identify the triple point and critical temperature on this diagram.

b)What phase change occurs when frozen carbon dioxide is warmed under 1 atm pressure?

c)What is the minimum pressure needed for liquid carbon dioxide to be stable?

d)The atmosphere on Mars has a surface pressure of about 0.007 atm and a temperature ranging from −143ºC to 27ºC. It consists of mostly carbon dioxide gas (95%), but some water vapour is present. Can liquid carbon dioxide exist on the Martian surface?

Explain why?

1