礦石、有限資源、回收利用：練習題

Which of the following statements provides the most accurate economic reason for the recycling of aluminium, rather than extracting it from its ore, bauxite?

Which of the following statements concerning metal ores and the conservation of metal resources are correct?

(1) Metals that are high in the reactivity series form more stable ores, which generally correlates with a later historical discovery of the metal.
(2) Recycling aluminium provides a more significant energy-saving benefit than recycling iron because the electrolytic extraction of aluminium is more energy-intensive than the reduction of iron ore with carbon.
(3) Metal recycling is considered a purely physical process because the scrap metal is already in the elemental state and does not require chemical changes.

The primary industrial production of aluminum from bauxite ore involves two major steps: the Bayer process to refine the ore to aluminum oxide ( $A{l}_2{O}_3$ ), followed by the highly energy-intensive Hall-Héroult process, which uses electrolysis and continuous consumption of carbon anodes to produce molten aluminum. Aluminum recycling is a well-established practice, requiring approximately 95% less electrical energy than the primary production route.

Considering the complete lifecycle of primary aluminum production compared to recycling, which of the following statements offers the most comprehensive chemical and environmental justification for prioritizing the use of recycled aluminum?

The table below provides energy data for the primary extraction (from ore) and secondary production (from recycling) of two metals, P and Q.

Metal P: Primary = \( 211 \text{ MJ kg}^{-1} \); Secondary = \( 12 \text{ MJ kg}^{-1} \)
Metal Q: Primary = \( 28 \text{ MJ kg}^{-1} \); Secondary = \( 9 \text{ MJ kg}^{-1} \)

Which of the following statements concerning these metals are correct?

(1) Metal P is likely to be higher than metal Q in the reactivity series.
(2) The percentage of energy saved by recycling is higher for metal P than for metal Q.
(3) Recycling is only necessary for metal P because its primary extraction is significantly more energy-intensive than that of metal Q.

While metal recycling offers significant environmental and economic benefits, the recycling of certain advanced metallic materials presents unique and substantial challenges. Which of the following factors is the most critical in complicating the large-scale, efficient recycling of complex alloys or rare metals embedded in advanced technological products?

In what chemical form are most metals found within their ores, and what general type of chemical process is required to obtain the pure metal?

Beyond conserving the finite supply of metal ores, identify one significant economic benefit and one significant environmental benefit of recycling metals when compared to extracting them from fresh ores.

State the key chemical concept that highlights why metal ores are considered a finite resource and briefly explain the practical necessity of metal recycling based on this concept.