Question

An element (A) belongs to period number 4 (four) and group number 11 (eleven) and is extracted from its pyrite ore. Element (A) reacts with oxygen at two different temperatures forming compounds (B) and (C). Element (A) also reacts with $conc.HN{{O}_{3}}$ to give compound (D) with the evolution of $N{{O}_{2}}$.Identify (A), (B), (C) and (D). Explain the reactions.

Answer 1

Copper pyrite, also known as Chalcopyrite is a copper ion sulfide which is an important ore of copper. It is a copper iron sulfide mineral that crystallizes in the trigonal system. The chemical formula of Chalcopyrite is $CuFe{{S}_{2}}$and has a brassy to golden yellow color.

Complete step by step solution:
-From knowledge of the periodic table, the element (A) which belongs to period number 4 and group number 11 is Copper.
-Copper is an element with the chemical symbol $Cu$, (derived from Latin name- Cuprum) having atomic number 29 is a soft, malleable, ductile metal with very high thermal and electrical conductivity.
-Copper does not react with water, but it does react with atmospheric oxygen slowly forming a layer of brown-black copper oxide.
-According to the question, copper reacts with oxygen at two different temperatures forming two different compounds (B) and (C). The reaction for such is given as-
$\begin{aligned} & 2Cu+{{O}_{2}}\xrightarrow{<1370K}2CuO(\text{Cupric oxide)} \\\ & 2Cu+{{O}_{2}}\xrightarrow{>1370K}2C{{u}_{2}}O(\text{Cuprous oxide)} \\\ \end{aligned}$
Let us name cupric oxide as compound (B) and cuprous oxide as compound (C).
-Now, the question says that the compound (A) also reacts with $conc.HN{{O}_{3}}$ giving the compound (D) with the release of $N{{O}_{2}}$ gas. The reaction for the same can be written as-
$Cu\xrightarrow{Conc.HN{{O}_{3}}}Cu{{(N{{O}_{3}})}_{2}}+N{{O}_{2}}+{{H}_{2}}O$

Hence, we can conclude that the compounds A, B, C, and D are Copper, Cupric oxide, Cuprous acid, and Cupric nitrate respectively.

Note: You should not get confused between cuprous and cupric oxide. Cupric oxide is considered as ‘fully oxidized’ whereas cuprous oxide is still in an active state. Since cuprous oxide is an active state compound it makes it extremely effective biocide as it still produces reactive oxygen species which are unstable molecules and can damage cell structures.