Model 3-­‐ Ternary Ionic Compounds Compound Name Cation Symbol and Anion symbol and Chemical Formula charges charges Ammonium NH4+ PO43-­‐ (NH4)3PO4 phosphate Barium nitrite Ba2+ NO2-­‐ Ba(NO2)2 +
2-­‐
Ammonium sulfate NH4 SO4 (NH4)2SO4 3+
2-­‐
Aluminum Al CO3 Al2(CO3)3 carbonate Iron(III) hydroxide Fe3+ OH-­‐ Fe(OH)3 Potassium nitrate K+ NO3-­‐ KNO3 1. How are ternary ionic compounds in Model 3 different from binary ionic compounds (NaCl, MgO, CaBr2, etc.) 2. Consider the compound iron(III) hydroxide in Model 3. a. how many hydroxide ions are combined with an Iron(III) b. Is your answer to part a the only combination of Iron(III) and hydroxide that should exist in nature. Explain 3. Consider the compound barium nitrite in Model 3. a. what does the subscripted 2 inside parentheses of the chemical formula tell you about the compound? b. What does the subscripted 2 outside parentheses of the chemical formula tell you about the compound? 4. How many atoms of each element are in one formula unit of ammonium phosphate? 5. A student writes the chemical formula for the ionic compound calcium hydroxide as CaOH2 a. Write the chemical formula for each ion in the compound b. Why is the student’s chemical formula for the compound calcium hydroxide wrong? 6. Many of the chemical formulas in Model 3 include parentheses. Which one of the following rules summarizes the appropriate use of parentheses in ternary ionic compounds? For the 3 rules that do not apply in all cases, show at least one counter example from the chemical formulas in Model 3. -­‐Parentheses are used around any ion that is used more than once in a formula unit -­‐Parentheses are used around any polyatomic ion -­‐Parentheses are used around any polyatomic ion used more than once in a formula unit. -­‐Parentheses are only used around polyatomic anions used more than once in a formula unit. 7. Fill out the table below: Ternary Ionic Compounds Name of the Formula of the Indic Indicate the Indicate Ionic compound ionic compound ate total the total the number of number of IC ions atoms ratio a. calcium CaSO4 1:1 2 6 sulfate b. copper(II) Cu(NO3)2 1:2 3 9 nitrate c. Lithium Li3PO4 3:1 4 8 phosphate KMnO4 1:1 2 6 d. Potassium permanganate
Al2(SO4)3 2:3 5 17 e. aluminum sulfate f. magnesium MgCO3 1:1 2 5 carbonate g. Mercury(I) Hg2(C2H3O2)2 1:2 3 16 acetate Barium sulfate h. BaSO4 1:1 2 6 Ammonium i. NH4NO3 1:1 2 9 nitrate Potassium j. K2CrO4 2:1 3 7 chromate Iron(II) nitrite k. Fe(NO2)2 1:2 3 7 Magnesium l. Mg(C2H3O2)2 1:2 3 15 acetate Aluminum m. Al2(CO3)3 2:3 5 14 carbonate 8. If you were asked to purchase sulfate from an on-­‐line chemical company, could you do so? Explain. 9. When asked to classify sodium acetate as either an ionic or covalent compound, a student responded with, “sodium acetate is both ionic and covalent.” Explain why the student gave this answer. Provide the chemical formula for the compound sodium acetate. Provide a model for the acetate ion.