Answer:
B) a substance's color and odor changed Explanation: A signal that a chemical change has occurred is when its odor (its smell) or its appearance has changed.
<h2>Answer:</h2>
The option B is correct option. Which is release of heat and/or light energy .
<h3>Explanation:</h3>
According to the definition of exothermic reaction :
<em>An exothermic reaction is a chemical reaction that releases energy by light or heat.</em>
From definition option B (release of heat and/or light energy) indicates that an exothermic reaction has taken place.
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<span>Both provide approaches to confirming the result of experimentation. Repetition can be developed by one scientist or team continually achieving the expected result but replication requires an independent person or team shows thay can arrive at the same answer independently</span>
Answer : The enthalpy of this reaction is, 0.975 kJ/mol
Explanation :
First we have to calculate the heat produced.
where,
q = heat produced = ?
m = mass of solution = 126 g
c = specific heat capacity of water = 
= initial temperature = 
= final temperature = 
Now put all the given values in the above formula, we get:
Now we have to calculate the enthalpy of this reaction.
where,
= enthalpy change = ?
q = heat released = 1.95 kJ
n = moles of compound = 2.00 mol
Now put all the given values in the above formula, we get:
Thus, the enthalpy of this reaction is, 0.975 kJ/mol
