Obtaining & Using Metals Flashcards
All 30 cards in this deck
State the reactivity series of metals from most to least reactive (including carbon and hydrogen).
Potassium, sodium, calcium, magnesium, aluminium, (carbon), zinc, iron, (hydrogen), copper, silver, gold.
Why is potassium higher in the reactivity series than calcium?
Potassium forms cations / loses its outer electron more easily.
What are the steps to deduce an order of reactivity from metals added to dilute acid?
e.g. magnesium, zinc and iron in dilute hydrochloric acid
- Use same-sized pieces of each metal in the same acid.
- Observe bubbling rate and temperature rise: magnesium bubbles vigorously and gets hot; iron bubbles slowly and barely warms.
- Most vigorous = most reactive: magnesium > zinc > iron.
True or false? Copper, silver and gold all react with cold water.
False. None of them react with cold water; calcium does.
Why does gold resist oxidation and stay shiny in jewellery?
Gold is at the bottom of the reactivity series, so it has very little tendency to lose electrons and form cations.
What would you see when excess zinc is added to blue copper sulfate solution?
A (red-)brown/orange/pink solid forms, some grey/silver solid remains, and the blue solution becomes colourless.
When will a metal displace another metal from its salt solution?
When the added metal is more reactive than the metal in the salt.
e.g. zinc displaces copper from copper sulfate.
In redox, what happens to electrons in oxidation and in reduction?
Oxidation is the loss of electrons; reduction is the gain of electrons.
What are the steps to identify what is oxidised and reduced in a displacement reaction?
e.g.
- Write the half equation for the metal: , so zinc is oxidised (loses electrons).
- Write the half equation for the metal ion: , so copper ions are reduced (gain electrons).
True or false? When copper oxide, CuO, reacts with sulfuric acid to form copper sulfate, the copper is reduced.
False. The copper ions are neither oxidised nor reduced — is present at the start and end.
In terms of oxygen, what are oxidation and reduction?
Oxidation is the gain of oxygen; reduction is the loss of oxygen.
Where are most metals found, and how are unreactive metals such as gold and silver found?
Most metals are found as ores (compounds) in the Earth's crust; unreactive metals are found as the uncombined elements.
How is the method of extracting a metal from its ore decided?
e.g. iron oxide and aluminium oxide
- Compare the metal with carbon in the reactivity series.
- Less reactive than carbon → heat the ore with carbon: iron.
- More reactive than carbon → electrolysis: aluminium.
True or false? Extracting a metal from its ore always involves reduction of the ore.
True. The metal ions gain electrons / the ore loses oxygen.
Give one advantage and one disadvantage of extracting a metal by electrolysis rather than heating with carbon.
Advantage: it can extract metals more reactive than carbon (e.g. aluminium), which carbon cannot reduce. Disadvantage: it uses a large amount of electricity, so it is expensive.
What is bioleaching?
Using bacteria to break down low-grade ores, producing a leachate solution containing metal compounds.
Give one disadvantage of bioleaching as a method of extracting metals.
It is very slow / low yield / toxic substances such as sulfuric acid can be produced / the leachate needs further processing.
Give one advantage of extracting a metal by phytoextraction rather than from its ore.
It decontaminates the ground / conserves ore reserves / allows use of low-grade ore / less noise from mining.
Give one disadvantage of phytoextraction as a method of extracting metals.
It is slow / needs a large area of land / only extracts metal from the ground surface / the metal still needs further extraction.
Give two economic/resource advantages of recycling metals rather than extracting them from ores.
It preserves finite ore reserves and uses less energy (less electricity).
Give two environmental advantages of recycling metals rather than mining and extracting them.
Less carbon dioxide emitted (less fossil fuel burned) and less waste/landfill; mining also causes loss of habitat, noise and dust.
What are the four stages considered in a life cycle assessment (LCA) of a product?
Obtaining the raw materials, manufacturing the product, using the product, and disposing of the product.
What is assessed at each stage of a life cycle assessment?
The effect on the environment, e.g. energy used, resources used, and waste or pollution produced.
True or false? A product with the lowest environmental impact during use must have the lowest overall impact in a life cycle assessment.
False. All four stages must be totalled — raw materials, manufacture, use and disposal.
What is phytoextraction?
Using plants to absorb metal compounds from the soil, so the metal can later be recovered from the plants.
How is the metal obtained from the leachate produced by bioleaching?
Electrolysis of the solution, or adding a more reactive metal to displace it.
e.g. scrap iron added to a leachate containing copper ions leaves copper metal.
What are the products when a reactive metal reacts with water?
A metal hydroxide and hydrogen.
e.g. calcium + water → calcium hydroxide + hydrogen
Which metals in the reactivity series do not react with dilute hydrochloric or sulfuric acid?
Those below hydrogen: copper, silver and gold.
What is a metal ore?
Rock with a high enough proportion of a metal compound that the metal can be extracted at a profit.
e.g. haematite, which contains iron oxide.
Apart from lower energy costs, what economic benefit does a metal recycling industry bring?
Employment: people are needed to collect, sort and reprocess scrap metal. It can also save the cost of mining or importing new ore.