Obtaining & Using Metals Flashcards
All 37 cards in this deck
What is the reactivity series order (most to least reactive) from potassium to gold, including carbon and hydrogen?
Potassium, sodium, calcium, magnesium, aluminium, (carbon), zinc, iron, (hydrogen), copper, silver, gold.
Which metals react with cold water?
Potassium, sodium and calcium (the most reactive metals), forming a metal hydroxide and hydrogen.
What is produced when a metal reacts with a dilute acid?
A salt and hydrogen.
e.g. magnesium + hydrochloric acid → magnesium chloride + hydrogen
Why is a metal high in the reactivity series more reactive, in terms of cations?
Its atoms have a greater tendency to lose electrons and form cations (positive ions).
True or false? Copper reacts with dilute hydrochloric acid to give hydrogen.
False. Copper is below hydrogen in the reactivity series, so it does not react with dilute acids.
When equal-sized pieces of different metals are added to the same dilute acid, how do you deduce the order of reactivity?
The faster the bubbling (rate of hydrogen production), the more reactive the metal.
What is a displacement reaction of metals?
A more reactive metal takes the place of a less reactive metal in its compound (solution).
In terms of electrons, what are oxidation and reduction?
Oxidation is loss of electrons; reduction is gain of electrons (OIL RIG).
What are the steps to identify what is oxidised and reduced in a metal displacement reaction?
e.g. zinc + copper sulfate solution
- The metal added loses electrons → oxidised:
- The metal ion in solution gains electrons → reduced:
- State both: zinc is oxidised, copper ions are reduced.
What is a redox reaction?
A reaction in which oxidation and reduction happen at the same time.
True or false? In the reaction between zinc and copper sulfate solution, the sulfate ions are reduced.
False. The sulfate ions are spectator ions; the copper ions are reduced.
How can displacement reactions in salt solutions be used to order three metals by reactivity?
Place each metal in solutions of the other metals' salts; the metal showing the greatest number of reactions is the most reactive.
What is seen when excess zinc is added to blue copper sulfate solution?
A red-brown/pink solid forms, some grey solid remains and the blue solution becomes colourless.
What is an ore?
A rock containing enough of a metal compound to make extracting the metal worthwhile.
Why are gold and silver found in the Earth's crust as uncombined (native) elements?
They are very unreactive, so they do not readily react with other elements to form compounds.
In terms of oxygen, what are oxidation and reduction?
Oxidation is the gain of oxygen; reduction is the loss of oxygen.
Why is extracting a metal from its ore described as reduction?
Oxygen (or electrons are gained by the metal ions) is removed from the ore to leave the metal.
How do you decide whether a metal is extracted by heating with carbon or by electrolysis?
e.g. calcium
- Find the metal's position relative to carbon in the reactivity series: calcium is above carbon.
- Above carbon → electrolysis; below carbon → heat with carbon.
- So calcium is extracted by electrolysis.
Why can't aluminium be extracted by heating its oxide with carbon?
Aluminium is more reactive than carbon, so carbon cannot remove the oxygen (cannot displace aluminium).
Why is extraction by electrolysis more expensive than reduction with carbon?
Electrolysis uses large amounts of electrical energy (and the ore must be melted or dissolved).
Write the word equation for the extraction of iron by heating iron oxide with carbon, and say what is reduced.
iron oxide + carbon → iron + carbon dioxide; the iron oxide is reduced (carbon is oxidised).
How is a metal's resistance to oxidation related to its position in the reactivity series?
The lower a metal is in the reactivity series, the more resistant it is to oxidation/corrosion.
What is bioleaching?
Using bacteria to produce a solution (leachate) containing metal compounds from low-grade ores.
Give two disadvantages of bioleaching.
It is very slow and low yield; toxic substances such as sulfuric acid can be produced.
Give two disadvantages of phytoextraction.
It is slow and needs a large area of land; the metal compound still needs further extraction.
Give two advantages of biological methods of metal extraction over traditional mining.
They allow use of low-grade ores and conserve ore reserves; they cause less noise, dust and habitat damage from mining.
True or false? Bioleaching and phytoextraction produce pure metal directly.
False. The leachate or plant ash contains metal compounds that need further processing, e.g. displacement or electrolysis.
Give two economic advantages of recycling metals rather than extracting them from ores.
It uses less energy (less electricity/fuel) and preserves finite ore reserves for future use.
Give two environmental advantages of recycling metals.
Less fossil fuel burned so less carbon dioxide emitted; less mining waste and landfill, and less habitat loss, noise and dust from mining.
Why is recycling aluminium especially worthwhile?
Aluminium is extracted by electrolysis, which uses a great deal of electricity, so recycling saves much more energy.
True or false? Metal ores are a finite resource.
True. Ores cannot be replaced once used, so recycling preserves the supply of valuable raw materials.
True or false? Recycling a metal always uses no energy at all.
False. Energy is still needed to collect, sort and melt the metal, but usually much less than extraction from ore.
What is a life cycle assessment (LCA)?
An assessment of the effect on the environment of a product over its whole life, from raw materials to disposal.
What are the four stages considered in a life cycle assessment?
- Obtaining the raw materials
- Manufacturing the product
- Using the product
- Disposing of the product.
True or false? A life cycle assessment only considers the pollution made while the product is being manufactured.
False. It also considers obtaining the raw materials, using the product and disposing of it.
Why can a life cycle assessment be difficult to make objective?
Some impacts (e.g. pollution effects) must be estimated or given a value judgement rather than measured.
In an LCA, which disposal route reduces environmental impact most for a metal product?
Recycling the metal, as it avoids landfill and saves the energy of extracting new metal.