Praseodymium: reactions of elements
Reaction of praseodymium with air
Praseodymium metal tarnishes slowly in air and burns readily to form a praseodymium oxide which has the approximate formula Pr6O11.
12Pr + 11O2 → 2Pr6O11
Reaction of praseodymium with water
The silvery white metal praseodymium is quite electropositive and reacts slowly with cold water and quite quickly with hot water to form praseodymium hydroxide, Pr(OH)3, and hydrogen gas (H2).
2Pr(s) + 6H2O(g) → 2Pr(OH)3(aq) + 3H2(g)
Reaction of praseodymium with the halogens
Praseodymium metal reacts with all the halogens to form praseodymium(III) halides. So, it reacts with fluorine, F2, chlorine, Cl2, bromine, I2, and iodine, I2, to form respectively praseodymium(III) bromide, PrF3, praseodymium(III) chloride, PrCl3, praseodymium(III) bromide, PrBr3, and praseodymium(III) iodide, PrI3.
2Pr(s) + 3F2(g) → 2PrF3(s) [green]
2Pr(s) + 3Cl2(g) → 2PrCl3(s) [green]
2Pr(s) + 3Br2(g) → 2PrBr3(s) [green]
2Pr(s) + 3I2(g) → 2PrI3(s)
Reaction of praseodymium with acids
Praseodymium metal dissolves readily in dilute sulphuric acid to form solutions containing the green aquated Pr(III) ion together with hydrogen gas, H2. It is quite likely that Pr3+(aq) exists as largely the complex ion [Pr(OH2)9]3+
2Pr(s) + 3H2SO4(aq) → 2Pr3+(aq) + 3SO42-(aq) + 3H2(g)