How to determine wether the given acid is reducing or oxidising?
Answers
Answer:
That depends on the oxidation state of the central Atom of the concerned acid, if the central atom is in its highest possible oxidation state it will not act as a reducing agent eg. H2SO4 (S +6) or HNO3, HIO4, HClO4 etc. But if the central atom is not in its highest oxidation state then it can act as a reducing agent (H2SO3 or HNO2 acts as a reducing agent) also acids like HBr or HI act as a reducing agent for Chlorine (addition of Cl2 in HBr or HI will lead to the formation of HCl and the respective halogen, similar reaction also happens if other strong oxidising agents are used). Another aspect to note that protic acids almost always act as an oxidising agent (due to proton) if allowed to react with a sufficiently electropositive element (eg. Na, K, Ca etc)
Answer:
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Definitions
A reducing agent reduces other substances and loses electrons; therefore, its oxidation state increases.
An oxidizing agent oxidizes other substances and gains electrons; therefore, its oxidation state decreases
Table 1: Commons oxidizing and reducing agents
Common oxidizing agents
Common reducing agents
O2
H2
O3
CO
F2
Fe
Br2
Zn
H2SO4
Li
Halogens (they favor gaining an electron to obtain a noble gas configuration)
Alkali metals (they favor losing an electron to obtain a noble gas configuration)
To help eliminate confusion, there is a mnemonic device to help determine oxidizing and reducing agents.
OIL RIG:
Oxidation Is Loss and Reduction Is Gain of electrons
Example 1: Identify reducing and oxidizing agents
Identify the reducing and oxidizing agents in the balanced redox reaction:
Cl2(aq)+2Br−(aq)→2Cl−(aq)+Br2(aq)(1)
Oxidation half reaction
2Br−(aq)→Br2(aq)(2)
Oxidation States: -1 0
Reduction Half Reaction
Cl2(aq)→2Cl−(aq)(3)
Oxidation States: 0 -1
Overbite
B- loses an electron; it is oxidized from Br- to Br2; thus, Br- is the reducing agent.
Cl2 gains one electron; it is reduced from Cl2 to 2 Cl-; thus, Cl2 is the oxidizing agent.
Exercise
Identify the oxidizing agent and the reducing agent in the following redox reaction:
MnO−4+SO2−3→Mn+2+SO2−4(4)
Solution
S is the reducing agent and Mn is the oxidizing agent.
Applications
Oxidizing and reducing agents are important in industrial applications. They are used in processes such as purifying water, bleaching fabrics, and storing energy (such as in batteries and gasoline). Oxidizing and reducing agents are especially crucial in biological processes such as metabolism and photosynthesis. For example, organisms use electron acceptors such as NAD+ to harvest energy from redox reactions as in the hydrolysis of glucose:
C6H12O6+2ADP+2P+2NAD+→2CH3COCO2H+2ATP+2NADH(1)
All combustion reactions are also examples of redox reactions. A combustion reaction occurs when a substance reacts with oxygen to create heat. One example is the combustion of octane, the principle component of gasoline:
2C8H18(l)+25O2(g)→16CO2(g)+18H2O(g)(2)
Combustion reactions are a major source of energy for modern industry.
Summary
By looking at each element's oxidation state on the reactant side of a chemical equation compared with the same element's oxidation state on the product side, one can determine if the element is reduced or oxidized, and can therefore identify the oxidizing and reducing agents of a chemical reaction.