What mass of natural gas (ch4) must you burn to emit 269 kj of heat? ch4 (g) + 2o2 (g) âco2 (g) + 2h2o (g) Î'hârxn=â802.3kj express the mass in grams to three significant figures?

When we have ΔH = - 802.3KJ, Negative charge so we can treat the heat as a product of the reaction as the following:

CH4 (g) + 2O2 (g) → CO2 (g) + 2H2O + 802.3KJ

when the enthalpy change is quoted per mole. and 1mole of CH4 give 802.3KJ

1molCH4→802.3KJ

? ← 269 KJ

So how many moles of CH4 if 269 KJ is generated?

moles of CH4 = 269KJ*1mol / 802 = 0.33 mol

and when we have the molar mass of CH4 = 16, we can get the mass from this formula:

Mass of CH4 = no of moles * molar mass

= 0.33 * 16 = 5.24 g