Descriptions of Chemical Changes (Reactions)

  1. Colorless hydrogen gas was mixed with colorless oxygen gas. Spark was introduced into the system. Rapid exothermic reaction occurred. Water vapor was produced. [H2(g) + O2(g) H2O(g) + Q]
  2. Elemental sulfur (S8) with yellow color was burned in the air. The oxygen in the air reacted with sulfur element to form sulfur trioxide. [S8(S) + O2(g) SO3(g)]
  3. Upon heating, solid mercury(II) oxide decomposes into liquid mercury metal and releases oxygen gas in the process. [HgO(s)Hg(l) + O2(g)]
  4. Hydrochloric acid (HCl) aqueous solution was added to zinc metal. Gas bubbles formed. Subsequent analysis on the gas produced indicated that it was hydrogen gas. In addition, aqueous solution containing zinc chloride was also produced. [Zn(s) + HCl(aq) ZnCl2(aq) + H2(g)]
  5. When a small piece of shining sodium metal was added to water containing phenolphthalein pH indicator, gas bubbles formed and the sodium metal piece quickly became smaller and disappeared. Solution quickly turned pink in color. The gas released was subsequently analyzed to be hydrogen gas. And the other product was sodium hydroxide which turned the phenolphthalein indicator pink. [Na(s) + H2O(l)NaOH(aq) + H2(g)]
  6. Photosynthesis process is used by all the plant species to produce sugar (C6H12O6). Plants use carbon dioxide and water to produce sugar (C6H12O6) and oxygen gas simultaneously. [CO2(g) + H2O(l)C6H12O6(s) + O2(g)]
  7. Aqueous solution of iron(III) sulfate was mixed with potassium hydroxide solution. White precipitate was observed to form immediately upon mixing. The white precipitate was subsequently analyzed to be iron(III) hydroxide, and aqueous solution of potassium sulfate was produced simultaneously. [Fe2(SO4)3(aq) + KOH (aq)  Fe(OH)3(p) + K2SO4(aq)]
  8. Solid aluminum reacts violently with solid iron(II) oxide to form aluminum oxide and elemental iron. [2Al(s) + 3FeO(s) Al2O3(s) + Fe(s)]
  9. Phosphorus element (P4) reacts with oxygen gas in air to form diphosphoruspentaoxide compound. [P4(s) + O2(g) P2O5(g)]
  10. When dilute hydrochloric acid was added to solid sodium carbonate powder, gas bubble formed. The gas produced was later analyzed to be carbon dioxide. Meanwhile, aqueous sodium chloride solution and pure water were produced. [Na2CO3(s) + HCl(aq)NaCl(aq) + H2O(l) + CO2(g)]
  11. When concentrated sulfuric acid (H2SO4) was slowly added to hydrogen iodide, dihydrogen sulfide gas, purple iodine solid and water were produced. [H2SO4(aq)+ HI(aq) H2Sg) + I2(s) + H2O(l)]
  12. Iron rusts when exposed to the outside elements. Chemical change associated with the rusting is that elemental iron reacts with oxygen gas to form reddish iron(III) oxide. [Fe(s) + O2(g) Fe2O3(s)]
  13. Very few chemical reactions involve noble gases. Here’s one: xeon gas is mixed with fluorine gas, the reaction is initiated by an electrical spark. Xeon hexafluoride is the sole product. [Xe(g)+F2(g) XeF6(g)]
  14. Propane (C3H8) is the common fuel used in outdoor barbeque. Combustion is the chemical change propane undergoes to release large amount of heat. The other reactant is oxygen gas, and products are carbon dioxide gas and water vapor. [C3H8(g) + O2(g) CO2(g) + H2O(g)]
  15. Solid potassium chlorate is thermally unstable. Under heating, it decomposes into potassium chloride powder and releases oxygen gas. [KClO3(s) KCl(s) + O2(g)]
  16. Hydrogen peroxide solution decomposes spontaneously into liquid water and oxygen gas upon addition of trace amount of iron catalyst. [H2O2(l) H2O(l) + O2(g)]
  17. Hydrofluoric acid (HF) dissolves solid silicon dioxide to form silicon tetrafluoride gas and pure water. [SiO2(s) + HF(aq) SiF4(g) + H2O(l)]