Final answer:
In the given exothermic reaction, when 18g of Carbon (C) reacts, about 590.3 kJ of heat is evolved.
Step-by-step explanation:
In this question, we're asked to calculate how much heat is evolved when 18 g of Carbon (C) reacts in an exothermic reaction. The given reaction, C(s) + O2(g) ---> CO2(g) ΔH = -393.5 kJ, is exothermic, meaning it releases heat. ΔH is negative, confirming this. We can use this to calculate the heat evolved for 18g of C. One mole of C (12g) releases 393.5 kJ of heat, so 18g of C would release more.
To solve, we set up a proportionality: 12g of C is to 393.5 kJ as 18g of C is to X kJ. Solving for X gives us X = (18g * 393.5 kJ) / 12g, which equals roughly 590.3 kJ. Therefore, when 18g of Carbon reacts, about 590.3 kJ of heat is evolved, and this reaction is exothermic.
Learn more about Exothermic Reactions