MC test: Metals & ICP spectroscopy

Multiple choice test on A.2 Metals & ICP spectroscopy

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.

The production of aluminium from alumina by electrolysis produced 54 kg of aluminium. If the same charge was passed through molten sodium chloride what mass of sodium would be produced?

The amount of Na produced in moles will be three times as much as Al. Since two mol of Al were formed 6 mol of Na will be formed.

 

Which metal cannot be obtained by heating its oxide in the presence of carbon?

Calcium is above carbon in the reactivity series so its oxide cannot be reduced by carbon. It is usually obtained by electrolysis.

 

Which substance is used to make the anode (+) for the industrial production of aluminium from alumina?

The anode is made of graphite. It needs to be replaced periodically as it is oxidised to carbon dioxide.

 

Which are correct statements about alloys?

I. Alloys are heterogeneous mixtures of metals with other metals or non-metals.

II. Brass is an alloy of copper and zinc.

III. Alloys are generally less ductile and less malleable than pure metals.

Alloys are homogeneous mixtures of metals with other metals or non-metals.

 

The graph shows a calibration curve for the concentration of nickel determined by ICP-OES.

A sample from a fertiliser gave an intensity reading of 8 x 105. What was the  concentration of Ni2+in the sample?

The intensity scale ranges from 0 to 2 x 106 so by interpolation an intensity reading of 8 x 105 gives a concentration of 1.9 mg dm−3.

 

Which property of a metal produces a very small magnetic field in opposition to an external magnetic field?

Metal that create a very small magnetic field in opposition to an external magnetic field are diamagnetic and contain no unpaired electrons.

 

ICP-OES was used to determine the concentration of both nickel and lead in a sample. The calibration curve obtained for nickel is shown.

Which statements will be true for the calibration curve for lead?

I. The wavelength used to make the measurements will be the same.

II. The intensity will be plotted on the vertical axis.

III. The graph will be a best fit straight line.

The plot will still be of intensity against concentration but it will be measured at a different wavelength as each metal emits radiation with a different characteristic energy.

 

What is the function of the cryolite used in the production of aluminium by electrolysis?

The alumina does not melt. Instead it forms a solution (but not an aqueous solution) in the molten cryolite so the Al3+ ions are free to move at a much lower temperature than the melting point of alumina.

 

Which gas is typically used to create the plasma in ICP spectroscopy?

Argon (at a temperature of around 6000 -10000°K) is an excellent source of ions so is the gas most typically used to create the plasma.

 

Which metal was not discovered until the nineteenth century?

Sodium was discovered in 1807 by Humphry Davy. The discovery of electricity was needed before metals high in the activity series (such as sodium) could be obtained from their molten ores by electrolysis.

 

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