Question 2.12: Recognizing Incorrect Names and Formulas of Ionic Compounds ......
Recognizing Incorrect Names and Formulas of Ionic Compounds
Problem Explain what is wrong with the name or formula at the end of each statement, and correct it:
(a) Ba(C_2H_3O_2)_2 is called barium diacetate.
(b) Sodium sulfide has the formula (Na)_2SO_3.
(c) Iron(II) sulfate has the formula Fe_2(SO_4)_3.
(d) Cesium carbonate has the formula Cs_2(CO_3).
Solution (a) The charge of the Ba^{2+} ion must be balanced by two C_2H_3O_2^− ions, so the prefix di- is unnecessary. For ionic compounds, we do not indicate the number of ions with numerical prefixes. The correct name is barium acetate.
(b) Two mistakes occur here. The sodium ion is monatomic, so it does not require parentheses. The sulfide ion is S^{2−}, not SO_3^{2−} (which is sulfite). The correct formula is Na_2S.
(c) The roman numeral refers to the charge of the ion, not the number of ions in the formula. Fe^{2+} is the cation, so it requires one SO_4^{2−} to balance its charge. The correct formula is FeSO_4. [Fe_2(SO_4)_3 is the formula for iron(III) sulfate.]
(d) Parentheses are not required when only one polyatomic ion of a particular kind is present. The correct formula is Cs_2CO_3.