Question

Which of the following sets of metals can form an alloy?
(A) $Cu$ and $Au$
(B) $Li$ and $Na$
(C) $Fe$ and $Hg$
(D) All of the above

Answer 1

Hint : It is observed that transition metals can form homogenous mixtures with one another in molten state. This homogenous mixture is known as alloy. Alloys are superior in physical properties of their parent metals.

Complete Step By Step Answer:
Copper $Cu$ and gold $Au$ are transition elements which have very similar atomic sizes and thus they can replace each other’s atom from the interstitial positions in their lattice; in this case replaces $Cu$ some of the $Au$ atoms in its lattice and thus forms a very stable compound which provides more strength and elasticity to $Au$ . Only alloyed gold can be used to make jewelry as it is too soft.
It is chemically represented as $Cu-Au,{ }CuAu,{ }C{{u}_{3}}Au,$ or auric cuprite.
$Li$ And $Na$ are alkali metals which have very high ionic character which are held by very strong lattice structure so there is very less chances of interstitial displacement hence they can’t form alloys.
$Fe$ And $Hg$ are both transition metals, and mercury $Hg$ is known for its amalgamating compounds. Moreover, both these atoms are of the same size. Still they don’t form alloys because of the bond structure of $Fe$ . $Fe$ bonds are so strong that they don’t allow $Hg$ atoms to diffuse into their lattice structure.
Option (A) is the correct option.

Additional Information:
Alloy formation between two or more metals changes the microstructure of the elements thereby bringing about physical as well as sometimes chemical differences in alloys from the pure metals.
Alloys generally improve strength and ductility of the material; improve malleability and toughness, alter the resistivity and other electrical properties, enhance the heat resistance and melting points and most importantly, build corrosion-resistant capability in metals.

Note :
$Cu-Au$ alloy is stable and improves the hardness and toughness of pure gold. This gold can be used to make ornaments and used in other applications. Hence, gold ornaments’ purity depends upon the amount of $Cu$ or $Ag$ mixed in it. This is defined in carat value. 24 carat gold refers to 99% pure gold.