In the presence of excess oxygen, methane gas burns in a constant-pressure system Calculate the value of q (kJ) in this exothermic reaction when 1.90 g of methane is combusted at constant pressure. to yield carbon dioxide and water: CH4 (g) + 2O2 (g) → CO2 (g) + 2H2O (l) ΔH = -890.0 kJ Calculate the value of q (kJ) in this exothermic reaction when 1.90 g of methane is combusted at constant pressure. Calculate the value of q (kJ) in this exothermic reaction when 1.90 g of methane is combusted at constant pressure. Calculate the value of q (kJ) in this exothermic reaction when 1.90 g of methane is combusted at constant pressure. Calculate the value of q (kJ) in this exothermic reaction when 1.90 g of methane is combusted at constant pressure. Calculate the value of q (kJ) in this exothermic reaction when 1.90 g of methane is combusted at constant pressure.