1 Each square on the map is 2 cm by 2 cm (4 cm 2) and represents 1 km 2 on the surface of the earth. 2  For 1:25,000 maps, the grid lines are 4 cm apart. 3  Each square on the map is 4 cm by 4 cm (16 cm 2) and represents 1 km 2 on the surface of the earth.
+ 2 e â + 2 H + â. In the last example, H + ions (hydrogen ions) also take part in the reaction, and are provided by an acid in the solution, or by the solvent itself (water, methanol etc.). Electrolysis reactions involving H + ions are fairly common in acidic solutions.
As each water molecule contains one atom of Oxygen and two atoms of Hydrogen you would expect electrolysis of water to produce twice as much Hydrogen as Oxygen.