Sodium hydroxide
| Acid | Alkali |
| In the presence of water, an acid will ionise to form hydrogen ion, H+. | In the presence of water, an alkali will ionise to form hydroxide ion, OH -. |
| Sour in taste | Bitter in taste |
| pH values less than 7 | pH values more than 7 |
| Indicator: Blue litmus paper (Red) | Indicator: Red litmus paper (Blue) |
| Indicator: Universal indicator (Orange and red) | Indicator: Universal indicator (Blue and purple) |
| Indicator: Methyl orange (Red) | Indicator: Methyl orange (Yellow) |
| React with bases to produce salts and water. 2HCl(aq) + CuO(s) –> CuCl2(aq) + H2O(l) | React with acids to produce salts and water. NaOH(aq) + HCl(aq) –> NaCl(aq) + H2O(l) |
| React with metals (reactive metal, higher position than H+ in the electrochemical series) to produce salts and hydrogen gas. 2HCl(aq) + Zn(s) –> ZnCl2(aq) + H2(g) | React with an ammonium salt (alkali is heated) to produce ammonia gas. Ba(OH)2(aq) + 2NH4Cl(s) –> BaCl2(aq) + 2H2O(l) + 2NH3(g) |
| React with carbonates to produce salts, carbon dioxide gas and water. H2SO4(aq) + ZnCO3(s) –> ZnSO4(aq) + H2O(l) + CO2(g) | React with aqueous salt solutions to produce metal hydroxides (as precipitate). 2NaOH(aq) + CuSO4(aq) –> Na2SO4(aq) + Cu(OH)2(s) |
