Explanation:
At present, 118 elements are known to us. All these have different properties. Out of these 118, only 94 are naturally occurring. As different elements were being discovered, scientists gathered more and more information about the properties of these elements.
In this redox reaction, the Cu goes from oxidation state of (0) to (+2), therefore it oxidises. N in HNO₃ goes from oxidation state of (+5) to N in NO with oxidation state of (+2) and becomes reduced.
Cu acts as the reducing reagent and HNO₃ is the oxidising agent.
oxidation half reaction
Cu ---> Cu²⁺ + 2e --1)
reduction half reaction
4H⁺ + 3e + NO₃⁻ ---> NO + 2H₂O --2)
to balance the number of electrons , 1) x3 and 2) x2
3Cu ---> 3Cu²⁺ + 6e
8H⁺ + 6e + 2NO₃⁻ ---> 2NO + 4H₂O
add the 2 equations
3Cu + 8H⁺ + 2NO₃⁻ ---> 3Cu²⁺ + 2NO + 4H₂O
add 6 nitrate ions to both sides to add up to 8 and form acid with 8H⁺ ions
3Cu + 8HNO₃ ---> 3Cu(NO₃)₂ + 2NO + 4H₂O
Balanced equation for the redox reaction is as follows;
3Cu(s) + 8HNO₃(aq) → 3Cu(NO₃)₂(aq) + 2NO(g) + 4H₂O<span>(l)
NO has a coefficient of 2
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The correct option is C.
An atom can be either in the ground state or in an excited state. An atom is said to be in the ground state, if the total energy of its electron can not be lowered by moving one or more electrons into different orbitals. At the ground state, the electrons in the atom have the lowest energy possible and they are stable. On the other hand, an atom is said to be in an excited state, if the energy of its electrons can be lowered by transferring one or more electrons into different orbitals. An atom in an excited state has more energy and is less stable.
<span> A </span>mixture<span> is made from </span>two<span> or more substances that are chemically unlike</span><span> and are not chemically joined. A </span>compound<span> is a substance formed when </span>two<span> or more elements chemically react with each other to ... substances because no new substance is formed, therefore they do not </span>have<span> any fixed properties.</span>
