Totally confused on the steps

Question

The combustion of hexane is given by the following reaction.

2 C₆H₁₄ + 19 O₂  12 CO₂ + 14 H₂O

The enthalpy of reaction is −4163.0 ^kJ/_mol. How much energy (in joules) will be released if 53.70 grams of hexane is burned. (Molar mass of hexane = 86.20 ^g/_mol). 

Answer 1

The enthalpy of reaction (-4163 kJ/mol) tells us that for every 2 moles of C6H14 (hexane) that is combusted, that is the amount of heat energy released.

So, step 1, is to find the number of moles of hexane being combusted:

53.70 g hexane x 1 mol hexane / 86.20 g = 0.62297 moles hexane.

Step 2 is to convert this to heat released:

0.62297 mols hexane x -4163 kJ / 2 moles = 1296.7 kJ

Final step is to convert this to joules and report to the correct number of sig. figs.:

1296.7 kJ x 1000 J / kJ = 1296700 J = 12,970 J = 1.297x10⁴ (4 sig. figs.)