June 2018 NY Regents Chemistry Exam
38 Given the equation representing a reaction: Mg(s) + 2HCl(aq) → MgCl2(aq) + H2(g)
Which type of chemical reaction is represented by the equation?
(1) synthesis
(2) decomposition
(3) single replacement
(4) double replacement
Solution: In synthesis two or more molecules come together to form one bigger molecule: A+B--> AB
Decomposition is the opposite of synthesis: AB --> A+B
In a single replacement reaction, one element replaces another: A +BC --> B +AC
In a double replacement reaction partners get exchanged: AB +CD --> AD +CB
Answer: 3
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