2 Reactions with water and oxygen

Group 2 reactions Reactivity of group 2 metals increases down the group Mg will also react slowly with oxygen without a flame. Mg ribbon will often have a thin layer of magnesium oxide on it formed by reaction with oxygen. 2Mg + O2  2MgO This needs to be cleaned off by emery paper before doing reactions with Mg ribbon. If testing for reaction rates with Mg and acid, an un-cleaned Mg ribbon would give a false result because both the Mg and MgO would react but at different rates. Mg + 2HCl  MgCl2 + H2 MgO + 2HCl  MgCl2 + H2O Reactions with oxygen. The group 2 metals will burn in oxygen. Mg burns with a bright white flame. 2Mg + O2  2MgO MgO is a white solid with a high melting point due to its ionic bonding. N Goalby chemrevise.org 1 Reactions with water. Magnesium burns in steam to produce magnesium oxide and hydrogen. The Mg would burn with a bright white flame. Mg (s) + H2O (g)  MgO (s) + H2 (g) The other group 2 metals will react with cold water with increasing vigour down the group to form hydroxides. Ca + 2 H2O (l) Ca(OH)2 (aq) + H2 (g) Sr + 2 H2O (l) Sr(OH)2 (aq) + H2 (g) Ba + 2 H2O (l) Ba(OH)2 (aq) + H2 (g) The hydroxides produced make the water alkaline (if they are soluble in water) One would observe: fizzing, (more vigorous down group) the metal dissolving, (faster down group) the solution heating up (more down group) and with calcium a white precipitate appearing (less precipitate forms down group) Mg will also react with warm water, giving a different magnesium hydroxide product. Mg + 2 H2O  Mg(OH)2 + H2 This is a much slower reaction than the reaction with steam and there is no flame.