Answer:
B. It undergoes a physical change.
Explanation:
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In this case, since we know that chemical changes lead to the formation of new atoms and/or compounds due to the bonds rearrangement of the initial substances and the physical changes occur without changing the composition of the initial substances, we can infer that, since melting is a process that changes the phase of matter from solid to liquid without changing the identity of the initial substance, the answer to this question would be B. It undergoes a physical change. because the other options describe chemical changes.
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When the enthalpy value is given, we can calculate how much heat is use or produces in a given equation.
67.6 kCal ---> 67.6 kCal= 1 mol of reaction
1 mol of reaction= 1 mol of CO (based on the coefficient)
so 1 mole of CO gives us 67.6 kCal of heat.
calculation:
1 mol CO