The total mass of reactants equals 5.3 g plus 6.0 g, which is 11.3 g. The total mass of products equals 2.2 g plus 0.9 g plus 8.2 g, which is 11.3 g. Since reactant mass equals product mass, the ...
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Row NH4+: NH4NO3, (NH4)2SO4, (NH4)3PO4. Row Li+: LiNO3, Li2SO4, Li3PO4. Row Al3+: Al(NO3)3, Al2(SO4)3, AlPO4. Row Cu2+: Cu(NO3)2, CuSO4, Cu3(PO4)2. Each entry balances the positive and negative charges of the combining ions.
The resulting chemical formulae are Mg3N2, Li3N, Na2S and Al2O3. In each compound, the combining valencies of the metal and non-metal elements are criss-crossed to establish an electrically neutral ionic substance.
The calculated formula unit masses are 80 u for ammonium nitrate NH4NO3, 98 u for phosphoric acid H3PO4 and 84 u for sodium hydrogencarbonate NaHCO3, found by adding the individual atomic masses.
Option (iii) correctly represents the chloride ion Cl-. A neutral chlorine atom has 17 electrons with arrangement 2, 8, 7. Gaining one electron forms Cl- with 18 electrons distributed as 2, 8, 8 in three shells.