Identify the oxidation state of H in [tex]H _2(g)[/tex]. [tex]Mg ( s )+2 HBr ( aq ) \rightarrow MgBr _2( aq )+ H _2(g)[/tex]
A. +1
B. -1
C. 0
D. +2
E. -2
Answer (2)
The oxidation state of hydrogen in H 2 ( g ) is 0 because, in elemental form, all elements have an oxidation state of 0. Thus, the answer is 0 .
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The problem requires finding the oxidation state of H in H 2 ( g ) .
Recall that the oxidation state of an element in its elemental form is 0.
Therefore, the oxidation state of H in H 2 ( g ) is 0.
The final answer is 0 .
Explanation
Problem Analysis The problem asks us to determine the oxidation state of hydrogen (H) in its diatomic form, H 2 ( g ) . We are also given a chemical reaction, M g ( s ) + 2 H B r ( a q ) → M g B r 2 ( a q ) + H 2 ( g ) , but this information is not needed to determine the oxidation state of H in H 2 ( g ) .
Oxidation State Rules The oxidation state, also known as oxidation number, is a measure of the degree of oxidation of an atom in a chemical compound. It is defined as the hypothetical charge that an atom would have if all bonds to atoms of different elements were 100% ionic. By convention:
The oxidation state of an element in its elemental form is always 0.
The oxidation state of a monatomic ion is equal to the charge of the ion.
The sum of the oxidation states of all the atoms in a neutral molecule is 0.
The sum of the oxidation states of all the atoms in a polyatomic ion is equal to the charge of the ion.
Determining the Oxidation State Since H 2 ( g ) is the elemental form of hydrogen, its oxidation state is 0.
Examples
Understanding oxidation states is crucial in various fields, such as environmental science, where it helps in predicting the fate and transport of contaminants in soil and water. For example, knowing the oxidation state of iron can help determine whether it will be soluble and mobile in groundwater or precipitate out as a solid. In materials science, oxidation states are used to design and synthesize new materials with specific properties. For instance, the oxidation state of transition metals in catalysts affects their activity and selectivity in chemical reactions. In biology, oxidation states are essential for understanding redox reactions in metabolic pathways, such as cellular respiration, where glucose is oxidized to produce energy.
