June 2023 NY Regents Chemistry Exam

8 Based on Table *I*, which equation represents conservation of mass and energy?

Solution: First let's check which equation is balanced (same number of atoms of each element on both sides). Equation 1 has 2 oxygens on the left and 3 on the right and can be eliminated. Equation 2 is the same and can be eliminated as well. Table I shows the ΔH sign for different reactions. -ΔH means heat is released and should be on the product (right) side.

Answer: 4

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