11,13,15 and 17

11. According to Section 2.6, acid leaching is not suitable for ores containing high levels of CaCO3 or MgCO3 because these carbonates react with the acid. Write the main reactions that may occur when these carbonates are treated with sulfuric acid. 12. According to Section 2.6, hydrogen peroxide H2O2 has been used to oxidize uranium (IV) to uranium (VI). Write a balanced equation for the oxidation of UO2 to UO3 by hydrogen peroxide. 13. According to Section 2.6, potassium permanganate KMnO4 has been used to oxidize uranium (IV) to uranium (VI). Assuming that the permanganate is reduced to Mn2+, write a balanced equation for the oxidation of UO2 to UO3 in (a) an acidic solution and (b) in a basic solution. 14. In a basic solution, permanganate MnO4is usually reduced to MnO2 rather than Mn2+. Write an equation for the oxidation of UO2 to UO3 in a basic solution, assuming that the permanganate is reduced to manganese dioxide. 15. Sodium chlorate NaClO3 has been used to oxidize uranium (IV) to uranium (VI). Assuming that the chlorate is reduced to Cl, write a balanced equation for the oxidation of UO2 to UO3 in an acidic solution. 16. When added to uranyl solutions, magnesia MgO can precipitate uranium as a hydrated uranium trioxide UO3xH2O. Write a balanced equation for this reaction. (Hint: MgO is converted to Mg2+.) 17. Hydrogen peroxide H2O2 can precipitate uranium peroxide UO42H2O from solutions containing uranyl ion. Write a balanced chemical equation for the precipitation reaction in (a) acidic solution and (b) basic solution