Concerning the reaction $\mathrm{C} \text { (graphite) }+\mathrm{O}_{2}(\mathrm{~g}) \rightarrow \mathrm{CO}_{2}(\mathrm{~g}) \quad \Delta \mathrm{H}^{\circ}=-393 \mathrm{~kJ} / \mathrm{mol}$ how many grams of C(graphite) must be burned to release 275 kJ of heat
A) 0.70 g
B) 8.40 g
C) 12.0 g
D) 17.1 g
E) 22.3 g

Question

Quizplus · Accepted Answer

The balanced equation for the combustion of graphite (C) is:

C(graphite) + O2(g) → CO2(g)    ΔH = -394 kJ/mol

From this balanced equation, we can see that the combustion of one mole of C releases 394 kJ of heat. This means that the combustion of (275/394) = 0.697 moles of C would release 275 kJ of heat.

To calculate the mass of C that corresponds to 0.697 moles, we need to use the molar mass of C, which is 12.01 g/mol:

mass of C = (0.697 mol) x (12.01 g/mol) = 8.40 g

Therefore, the best choice is B) 8.40 g, as this mass of graphite would need to be burned to release 275 kJ of heat.

Concerning the Reaction How Many Grams of C(graphite) Must Be Burned to Release