MC test: Nanotechnology

Multiple choice test on A.6 Nanotechnology

Use the following 'quiz' to test your knowledge and understanding of this sub-topic. As this relates to a sub-topic on the options you may need access to the IB data booklet.

If you get an answer wrong, read through the explanation carefully to learn from your mistakes.

Which methods can be used to produce carbon nanotubes?

I. chemical vapour deposition

II. high pressure carbon monoxide

III. arc discharge

All three methods can be used.

 

What provides the nucleation surface for the transformation of carbon monoxide into carbon during the formation of carbon nanotubes when carbon monoxide is reacted with iron pentacarbonyl, Fe(CO)5, at high pressure and high temperature?

Under the reaction conditions Iron pentacarbonyl decomposes to form iron nanoparticles and carbon monoxide according to the equation Fe(CO)5(g) →  Fe(s) + 5CO(g). The iron nanoparticles form the transformation surface for the conversion of carbon monoxide into carbon during the formation of the carbon nanotubes: xCO(g) → CNT(s) + ½xCO2(g)

 

What do the letters AFM stand for when referring to the process of dip-pen nanolithography to manipulate and position individual atoms?

Atomic force microscopy (AFM) is a high resolution form of scanning probe microscopy used in dip-pen nanolithography.

 

Which two gases may be used in chemical vapour deposition to form carbon nanotubes?

In the CVD method carbon nanotubes are formed from methane (or another carbon-containing gas such as ethene or ethyne) in the plasma phase under the influence of a strong electric field with an inert gas, such as nitrogen, being used as the carrier gas.

 

What is range for the length of compounds that are typically included in nanotechnology?

The range is typically between one and one hundred nanometres, i.e. 1.0 x 10−9 m to 1.0 x 10−7 m.

 

Which properties are associated with carbon nanotubes?

I. High tensile strength

II. High electrical conductivity

III. High thermal insulation

Because they contain delocalized electrons carbon nanotubes have both high electrical conductivity and high thermal conductivity so they are poor thermal insulators.

 

Which statements are correct concerning the structure of carbon nanotubes?

I. The walls of the main cylindrical tube are made from C6 rings.

II. The tubes are closed at the end by a mixture of C5 and C6 rings.

III. All the carbon atoms in nanotubes are covalently bonded together.

The main walls are made of graphene which contains only hexagonal carbon rings. The ends are closed by a hemisphere of buckminsterfullerene which contains both pentagonal and hexagonal carbon rings. The exceptional high tensile strength of carbon nanotubes is due to the fact that all the carbon atoms are covalently bonded together and this strong bonding extends along the length of the tube.

 

What is the oxidation state of iron in iron pentacarbonyl, Fe(CO)5?

Carbon monoxide is a neutral molecule and since iron pentacarbonyl has no overall charge the oxidation state of iron must be zero.

 

Which material is often used to form the electrodes in a hydrocarbon solvent such as methylbenzene, C6H5CH3 when the arc discharge method is used to make carbon nanotubes?

Pure graphite is used for the electrodes for the arc discharge method when no solvent is present but when hydrocarbon solvents are used the electrodes are made of metal. The metal usually used is nickel as unlike sodium it has a high melting point (1455 oC) and is relatively inactive.

 

Which are concerns about the implications of nanotechnology?

I. The possible toxicity of nanoparticles

II.  Where the responsibility lies for regulating the control of nanotechnology

III. The safe disposal of waste nanoparticle material

Very small particles, such as those of asbestos, are already known to cause problems with the lungs so there is concern that nanoparticles may be toxic to humans. This means that any waste nanoparticle products need to be disposed of safely. Current regulations lag behind the developments of nanotechnology and decisions regarding funding and safety may require agreement between international bodies.

 

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