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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) ΔH = -890.0 kJ Calculate the value of q (kJ) in this exothermic reaction when 1.60 g of methane is combusted at constant pressure.

Respuesta :

Answer : The heat value of 'q' in exothermic reaction is -8900 kJ

Explanation :

First we have to calculate the number of moles of methane.

[tex]\text{Moles of methane}=\frac{\text{Mass of methane}}{\text{Molar mass of methane}}[/tex]

Molar mass of methane = 16 g/mole

[tex]\text{Moles of methane}=\frac{1.60g}{16g/mole}=0.1mole[/tex]

Now we have to calculate the heat released in the reaction.

[tex]\Delta H=\frac{q}{n}[/tex]

or,

[tex]q=\Delta H\times n[/tex]

where,

[tex]\Delta H[/tex] = enthalpy change = 890.0 kJ/mol

q = heat released = ?

n = number of moles of methane = 0.1 mol

Now put all the given values in the above formula, we get:

[tex]q=(-890.0kJ/mol)\times (0.1mol)=-8900kJ[/tex]

Therefore, the heat value of 'q' in exothermic reaction is -8900 kJ

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