What will be the change in enthalpy when 100.0 g of butane, C4H10, is burned in oxygen as shown in the thermochemical equation below?
2 C4H10(l) + 13 O2(g) → 8 CO2(g) + 10 H2O(g) ΔH = −5271 kJ
−1.817 × 104 kJ
To find the change in enthalpy when 100.0 g of butane is burned, we need to use the given thermochemical equation and the molar mass of butane.
First, calculate the number of moles of butane:
Molar mass of C4H10 = 4 * (12.01 g/mol) + 10 * (1.01 g/mol) = 58.12 g/mol
Number of moles of butane = mass of butane / molar mass of butane
= 100.0 g / 58.12 g/mol
= 1.719 mol
According to the stoichiometry of the balanced equation, the coefficient of butane is 2. This means that when 2 moles of butane are burned, the enthalpy change is -5271 kJ.
Now, calculate the change in enthalpy when 1.719 moles of butane are burned:
Change in enthalpy = (−5271 kJ / 2 mol) * 1.719 mol
= -4535.9 kJ
Therefore, the change in enthalpy when 100.0 g of butane is burned is approximately -4535.9 kJ.
The closest answer choice is -4534 kJ, so the correct answer is -4534 kJ.
Well, my friend, it seems like we've got ourselves a combustion reaction here! And the good news is, we've got all the necessary information to determine the change in enthalpy.
According to the thermochemical equation, the enthalpy change, ΔH, is -5271 kJ.
Now, since the equation shows the combustion of 2 moles of butane (C4H10), we need to determine the number of moles in 100.0 g of butane.
The molar mass of butane (C4H10) is approximately 58.12 g/mol, so we divide the mass by the molar mass to get the number of moles:
Moles of butane = 100.0 g / 58.12 g/mol ≈ 1.721 mol
Now, we compare the coefficients in the equation to find the ratio between butane and the change in enthalpy:
ΔH = -5271 kJ * (1 mol butane / 2 mol butane)
= -2635.5 kJ
So, the change in enthalpy when 100.0 g of butane is burned is approximately -2636 kJ.
And remember, my friend, when it comes to enthalpy changes, negative values mean the reaction is exothermic and positive values mean it's endothermic. In this case, it's a negative value, so it's quite the fiery reaction!
First find how many moles is 100.0g of butane. Divide 100.0g / 58.14.
So 1.72 mol of butane=-5271J.
The mol coefficient of butane C4H10 is 2.
So multiply the mole of butane by the coefficient to get -1.817*104kj