The chemical reactions given are all related to the element aluminum (Al). The reactions show how aluminum can react with oxygen (O) to form aluminum oxide (Al2O3), with potassium hydroxide (KOH) to form potassium aluminate (KAlO2), with chlorine (Cl) to form aluminum chloride (AlCl3), and with water (H2O) to form aluminum hydroxide (Al(OH)3). These reactions demonstrate the versatility of aluminum in forming different compounds with various elements.