OZ Multiple Choice Questions

Question 1

Which molecule is polar?

• BF₃
• _{<span>CO</span>2}
• _{<span>NH</span>3}
• _{<span>SO</span>3}

Answer 1

• _{<span>NH</span>3}

Question 2

What intermolecular forces are present between molecules of methanal, HCHO?

• instantaneous dipole–induced dipole bonds only
• hydrogen bonds and instantaneous dipole–induced dipole bonds
• permanent dipole–permanent dipole bonds only
• permanent dipole–permanent dipole bonds and instantaneous dipole–induced dipole bonds

Answer 2

• permanent dipole–permanent dipole bonds and instantaneous dipole–induced dipole bonds

Question 3

Hydrofluoroalkanes, such as CH₂F₂, have been considered as an alternative to CFCs.

Why are hydrofluoroalkanes preferable compounds?

• They do not have as high a greenhouse factor.
• They break down in the troposphere and do not reach the stratosphere, so do not damage the ozone layer.
• The bonds are not broken by UV radiation in the stratosphere, so they do not cause ozone depletion.
• They are less flammable and less toxic.

Answer 3

• The bonds are not broken by UV radiation in the stratosphere, so they do not cause ozone depletion.

Question 4

The Maxwell–Boltzmann distribution of energy for gaseous particles under two different sets of conditions, X and Y, is shown below.

Which statement can be deduced from the distribution?

• Y is at a lower concentration than X.
• X and Y are at different pressures.
• Y is in the presence of a catalyst.
• Y is at a higher temperature than X.

Answer 4

• Y is at a higher temperature than X.

Question 5

Samples of 1-chlorobutane, 1-bromobutane and 1-iodobutane are put into separate test tubes containing silver nitrate solution and then simultaneously placed into a warm water bath.

In what order are the coloured precipitates observed?

• whte, cream then yellow
• cream, yellow then white
• cream, white then yellow
• yellow, cream then white

Answer 5

• yellow, cream then white

Question 6

What is the role of the hydroxide ion in the reaction between aqueous sodium hydroxide and bromopropane?

• Base
• Electrophile
• Free Radical
• Nucleophile

Answer 6

• Nucleophile

Question 7

The bond dissociation enthalpy for a carbon–chlorine bond is approximately 330 kJ mol^–1.

What is the minimum frequency of light required to break one carbon–chlorine bond?

• 4.9 × 10³⁸ Hz
• 8.2 × 10¹⁴ Hz
• 8.2 × 10¹¹ Hz
• 1.2 × 10^-15 Hz

Answer 7

• 8.2 × 10¹⁴ Hz

Question 8

Which reaction is a stage necessary for the formation of ozone in the stratosphere?

• O₃ + UV –> O₂ + O•
• O₂ + UV –> 2O•
• O₃ + Cl• –> O₂ + ClO•
• ClO• + O^- –> O₂ + Cl^-

Answer 8

• O₂ + UV –> 2O•

Question 9

Chlorine radicals in the stratosphere act as catalysts for the reaction shown below.

O₃ + O• –> 2O₂

Which statement is true about the action of the chlorine radicals?

• They increase the number of collisions between ozone molecules and oxygen molecules.
• They act as heterogeneous catalysts.
• They are not used up during the process.
• They increase the energy of the collisions.

Answer 9

• They are not used up during the process.

Question 10

Which of the following statements can explain why the rate of a reaction increases in the presence of a suitable catalyst?

1. A greater proportion of reactant particles have sufficient energy to react.
2. Reactant particles collide with more energy.
3. Reactant particles collide more frequently.

• 1,2 and 3
• Only 1 and 2
• Only 2 and 3
• Only 1

Answer 10

• Only 1