| Test analysis: (1) the main component of bauxite (alumina), the aluminum element in the alumina shows +3 valence, the oxygen element shows -2 valence, and its chemical formula is Al 2 O 3. (2) the solute of vinegar commonly used at home is acetic acid, its chemical formula is: CH 3 COOH. (3) by the representation of ions, in the representation of the ion in the upper right-hand corner of the element symbols, the number of positive and negative charges of the ions, the number of numbers in the front, the positive and negative symbols in the back, with a charge of 1, 1 to be omitted. If more than one of the ion, the ion symbol in front of the corresponding number, so the magnesium ion can be expressed as: Mg 2+. (4) by the molecular representation, the correct writing of the chemical formula of the substance, that more than one of the molecule, in front of its chemical formula plus the corresponding number, then 5P 2 O 5 can be expressed as: five molecules of phosphorus pentoxide. (5) by the representation of atoms, the element symbols to indicate an atom, that more than one of the atom, in its element symbols before the corresponding number, so 3Hg is expressed as: three mercury atoms. Review: this question is not difficult, the main test students of common chemical terms (chemical formula, ion symbols, molecular symbols, atomic symbols, etc.) of the ability to write and understand. |