Extraction and Uses of Metals
6 marks · NormalTitanium is a metal above carbon in the reactivity series. Brass is an alloy of copper and zinc. Use your knowledge of methods of extraction and metals to answer the following questions.
Describe how titanium can be extracted from its compound when it cannot be reduced by carbon.
Brass is harder than pure copper.
State what is meant by the term "alloy."
Explain why alloys such as brass are usually harder than pure metals.
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(a) By heating titanium compound with a more reactive metal (such as sodium or magnesium). · must show heating with a more reactive metal, cannot use carbon
(b(i)) A mixture of a metal with one or more other elements (usually metals or carbon). · must show mixture, metal with other elements
(b(ii)) Different sized atoms in an alloy distort the lattice structure, which prevents layers of atoms/ions from sliding over each other easily, making them harder. · must show different sized atoms, distortion of lattice, harder because layers cannot slide
Common mistakes: Saying titanium is extracted by carbon reduction.; Not mentioning a mixture in definition of alloy.; Vague statements about hardness without atomic explanation.
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Marking points
M1 (a) · 1 mark · Refers to extraction by using a more reactive metal (e.g., sodium or magnesium).
A1 (a) · 1 mark · States carbon cannot be used or reason why (titanium is above carbon in reactivity).
B1 (b(i)) · 1 mark · Defines alloy as a mixture of metals (or metal with other elements).
M2 (b(ii)) · 1 mark · States that alloys contain different sized atoms/elements.
M3 (b(ii)) · 1 mark · Mentions that these distort/break up the regular lattice.
A2 (b(ii)) · 1 mark · Explains this prevents layers sliding or makes the alloy harder.
Worked solution
a) Titanium is above carbon in the reactivity series, so it cannot be extracted from its ore by reduction with carbon. Instead, it is extracted by heating titanium(IV) oxide with a more reactive metal such as magnesium or sodium. The more reactive metal displaces titanium from its compound.
b)(i) An alloy is a mixture of a metal with one or more other elements, usually other metals or carbon.
b)(ii) In a pure metal, all the atoms are the same size and arranged in a regular lattice, so layers can slide over each other easily, making the metal soft. In an alloy, the particles are different sizes, which distorts the regular lattice structure. This makes it difficult for the layers to slide over each other, so alloys are harder than pure metals.