January 2018 NY Regents Chemistry Exam
5 What is the chemical formula for ammonium sulfide?
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Solution: The formula for ammonium can be found in Table E on the Reference Table and is NH4+. Sulfide ion is S^2- (charge can be found on the Periodic Table). Next, we need to criss cross the powers to become subscripts.
NH4^+1 S^-2 = (NH4)2S1 = (NH4)2S
Answer: 1
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