August 2018 NY Regents Chemistry Exam
37 Given the balanced equation representing a reaction: 2H2 + O2 → 2H2O + energy Which type of reaction is represented by this equation? (1) decomposition (2) double replacement
(3) single replacement
(4) synthesis
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: 4
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