The resulting chemical formulae are CaBr2, Al2(CO3)3, K2SO4 and NH4Cl. In each ionic compound, the valency numbers are criss-crossed so that positive and negative charges balance out to maintain overall electrical neutrality.
Write the formulae of the compounds formed from the following pairs of ions. (i) Ca2+ and Br- (ii) Al3+ and CO3 2- (iii) K+ and SO4 2- (iv) NH4+ and Cl-
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For Ca2+ and Br-, criss-crossing the valencies gives calcium bromide as CaBr2. For Al3+ and CO3 2-, balancing charges requires two aluminium ions and three carbonate groups, producing Al2(CO3)3. For K+ and SO4 2-, two potassium ions balance one sulfate ion, yielding K2SO4. For NH4+ and Cl-, both have unit charges, producing ammonium chloride NH4Cl. All formulae represent fully neutral ionic compounds.
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