Question

One of the classic methods for the determination of the manganese content in steel involves converting all the manganese to the deeply colored permanganate ion and then measuring the absorption of light. The steel is first dissolved in nitric acid, producing the manganese(II) ion and nitrogen dioxide gas. This solution is then reacted with an acidic solution containing periodate ion; the products are the permanganate and iodate ions. Write balanced chemical equations for both of these steps.

Short answer

The balanced chemical equations for determining the manganese content in steel are: 1. $Mn(s)+2HN{O}_3(aq)\to M{n}^{2+}(aq)+2N{O}_2(g)+2H^{+}(aq)$ 2. $5M{n}^{2+}(aq)+12I{O}_4^{-}(aq)+16H^{+}(aq)\to 5Mn{O}_4^{-}(aq)+12I{O}_3^{-}(aq)+8H_{2}O(l)$

Step-by-step solution

Identify the chemical formulas

First, let us determine the chemical formulas for all the species involved in both reactions: 1. Steel: Primarily composed of Iron (Fe) and Manganese (Mn). 2. Nitric acid: HNO3 3. Manganese(II) ion: Mn^(2+) 4. Nitrogen dioxide gas: NO2 5. Periodate ion: IO4^(-) 6. Acidic solution: H+ ions are present, usually from a strong acid like H2SO4 or HCl. 7. Permanganate ion: MnO4^(-) 8. Iodate ion: IO3^(-) Now that we have the chemical formulas, we can write the unbalanced equations.

Write the unbalanced chemical equations

For the first reaction, Manganese in steel + Nitric acid -> Manganese(II) ion + Nitrogen dioxide gas Mn(s) + HNO3(aq) -> Mn^(2+)(aq) + NO2(g) For the second reaction, Manganese(II) ion + Periodate ion + Acidic solution -> Permanganate ion + Iodate ion Mn^(2+)(aq) + IO4^(-)(aq) + H+(aq) -> MnO4^(-)(aq) + IO3^(-)(aq)

Balance the chemical equations

Balance the first chemical equation: $Mn(s)+2HN{O}_3(aq)\to M{n}^{2+}(aq)+2N{O}_2(g)+2H^{+}(aq)$ Balance the second chemical equation: $5M{n}^{2+}(aq)+12I{O}_4^{-}(aq)+16H^{+}(aq)\to 5Mn{O}_4^{-}(aq)+12I{O}_3^{-}(aq)+8H_{2}O(l)$ Now we have the balanced chemical equations for determining the manganese content of steel: 1. $Mn(s)+2HN{O}_3(aq)\to M{n}^{2+}(aq)+2N{O}_2(g)+2H^{+}(aq)$ 2. $5M{n}^{2+}(aq)+12I{O}_4^{-}(aq)+16H^{+}(aq)\to 5Mn{O}_4^{-}(aq)+12I{O}_3^{-}(aq)+8H_{2}O(l)$