Answer: 
is a reactant; it is present before the reaction occurs.
Explanation:
In a chemical reaction the chemical formulas written before the arrow are described as reactants as they react together to form products which are written after the arrow.
Thus and HCl are reactants here whereas 
, 
and 
are products.
Answer:
When an atom attracts extra electrons it becomes a negative ion. The negative ion is larger than the original atom. The positive nucleus remains the same, with the same attractive force. However, this attractive force is now pulling on more electrons and therefore has less effect.
Or
Positive ions are formed by removing one or more electrons from the outermost region of the atom. The opposite is true of negative ions. When electrons are added to form an anion, the increased electron-electron repulsions cause the electrons to spread out more in space. Thus, anions are larger than their parent atoms.
The oxidation number sulfur in H₂S is -2.
A compound's total number of oxidations must be zero.
The two hydrogen atoms in the chemical hydrogen sulfide, H₂S, each have an oxidation number of +1, making a total of +2. As a result, the compound's sulfur has an oxidation number of -2, and the total number of oxidations is 0.
Assume that the sulfur atom in H₂S has an oxidation number of x.
S be x.
Now,
2+x=0
⇒x=−2
<h3>What is oxidation number?</h3>
The total number of electrons that an atom either receives or loses in order to create a chemical connection with another atom is known as the oxidation number, also known as the oxidation state.
Depending on whether we are taking into account the electronegativity of the atoms or not, these phrases can occasionally have a distinct meaning. Coordination chemistry commonly makes use of the phrase "oxidation number."
<h3>What distinguishes an oxidation number from an oxidation state?</h3>
In contrast to the oxidation state, which indicates how oxidised an atom is in a molecule, the oxidation number describes the charge that the core metal atom will retain once all ligands have been removed.
To know more about oxidation number:
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Answer: 1/12
1/4 divided by 3/1
KCF:Keep the first fraction, Change the sign to muplication, Flip the second fraction.
1/4* 31
1*1=1
4*3=12
1/12
