Extracting Metals and Equilibria

How can the relative reactivity of metals be determined?

By comparing their reactions with water, acids and salt solutions.

What is a displacement reaction?

A reaction where a more reactive metal displaces a less reactive metal from its compound.

Why are displacement reactions redox reactions?

The more reactive metal loses electrons (oxidation), while the less reactive metal ions gain electrons (reduction).

What is the reactivity series of metals from most to least reactive?

Potassium, sodium, calcium, magnesium, aluminium, carbon, zinc, iron, hydrogen, copper, silver, gold.

What does a metal's position in the reactivity series show?

Its relative tendency to form positive ions (cations).

Where are most metals found?

In ores in the Earth's crust.

Which metals can be found in the Earth's crust as uncombined elements?

Unreactive metals, such as gold.

What is oxidation in terms of oxygen?

Gain of oxygen.

What is reduction in terms of oxygen?

Loss of oxygen.

What happens to metal ores during extraction?

They are reduced to produce the metal.

How does a metal's position in the reactivity series affect its extraction method?

Metals below carbon can generally be extracted by heating their ores with carbon, while metals above carbon require electrolysis.

Why is aluminium extracted by electrolysis?

Aluminium is more reactive than carbon, so carbon cannot reduce aluminium oxide.

Why can iron be extracted using carbon?

Iron is less reactive than carbon, so carbon can reduce iron oxide to iron.

What is bacterial extraction of metals?

Using bacteria to help extract metals from ores.

What is phytoextraction?

Using plants to absorb metal ions from contaminated soil, then harvesting the plants to recover the metals.

What is an advantage of biological metal extraction?

It can use less energy and cause less environmental damage than some traditional extraction methods.

How is a metal's resistance to oxidation related to its reactivity?

Less reactive metals are more resistant to oxidation, while more reactive metals oxidise more easily.

Which metals are more resistant to oxidation?

Less reactive metals, such as gold and silver.

What are the advantages of recycling metals?

It reduces mining, saves energy and raw materials, reduces environmental damage and can have economic benefits.

How does recycling preserve valuable raw materials?

It allows existing metals to be reused instead of extracting new metals from ores.

What is a life-cycle assessment (LCA)?

An assessment of the environmental impact of a product throughout its entire life.

What four stages are considered in a life-cycle assessment?

Obtaining raw materials, manufacturing the product, using the product and disposing of the product.

What should be considered when evaluating data from a life-cycle assessment?

The environmental impacts at each stage and the overall environmental impact of the product.

What is a reversible reaction?

A reaction that can proceed in both the forward and reverse directions.

What symbol represents a reversible reaction?

⇌

How can the direction of some reversible reactions be altered?

By changing the reaction conditions, such as temperature, pressure or concentration.

What is dynamic equilibrium?

A state in a closed system where the forward and reverse reactions occur at equal rates, so the concentrations of reactants and products remain constant.

What are the reactants in the Haber process?

Nitrogen and hydrogen.

What is the equation for the Haber process?

Nitrogen + hydrogen ⇌ ammonia.

Where is nitrogen for the Haber process obtained from?

The air.

Where is hydrogen for the Haber process obtained from?

Natural gas.

What happens when the Haber process reaches dynamic equilibrium?

The forward and reverse reactions occur at equal rates, so the concentrations of reactants and products remain constant.

What temperature is used in the Haber process?

450°C.

What pressure is used in the Haber process?

200 atmospheres.

What catalyst is used in the Haber process?

Iron.

What factors can affect the position of a dynamic equilibrium?

Temperature, pressure and concentration.

What happens to equilibrium when the concentration of a reactant is increased?

The equilibrium shifts towards the products to oppose the increase in reactant concentration.

What happens to equilibrium when the concentration of a product is increased?

The equilibrium shifts towards the reactants to oppose the increase in product concentration.

What happens to equilibrium when pressure is increased?

It shifts towards the side with fewer gas molecules.

What happens to equilibrium when pressure is decreased?

It shifts towards the side with more gas molecules.

What happens to equilibrium when temperature is increased?

The equilibrium shifts in the endothermic direction, which absorbs heat.

What happens to equilibrium when temperature is decreased?

The equilibrium shifts in the exothermic direction, which releases heat.