In the presence of excess oxygen, methane gas burns in a constant-pressure system to yield carbon dioxide and water: CH4 (g) + 2O2 (g) → CO2 (g) + 2H2O (l) △H = -890.0 kJ Calculate the value of q (kJ) in this exothermic reaction when 1.80 g of methane is combusted at constant pressure.

-100.125

Explanation:

We are given

          CH4 (g) + 2O2 (g) → CO2 (g) + 2H2O (l)    △H = -890.0 kJ/mol

The given information is for complete reaction

we have 1.8grams of Methane

Molar mass of CH4 = 16  

No of moles of Methane = 1.8/ 16

                                          = 0.1125

So the amount of the heat will be released from the amount of the methane

Q = No of moles*( -890.0 kJ/mol)

  = 0.1125*(-890)

   = -100.125kJ/mole

Therefore the amount of Energy released from 1.8 grams of methane is equal to -100.125

the temperature of the gas, in k, not celsius.