We know the next following bond energies: C≡O: 1 075 kJ; H−H: 435 kJ; C−H: 393 kJ; C−O: 356 kJ; O−H: 464 kJ. With that, a) Calculate how many kJs of energy are required to break all the simple bonds in 0,2 moles of CH4. b) With the energy bonds, do a estimation of the energy released in the following reaction: CO (g) + 2 H2 (g) → CH3OH
To calculate the total energy required to break all the simple bonds in 0.2 moles of CH4, we need to determine the number of each type of bond in CH4 and then multiply it by their respective bond energies.
a) Let's start by analyzing the structure of CH4 (methane):
- CH4 has four C−H bonds since it contains four hydrogen atoms bonded to a central carbon atom.
Now, let's calculate the total energy required to break all the C−H bonds in 0.2 moles of CH4:
1 mole of CH4 contains 4 moles of C−H bonds (according to the ratio of atoms in CH4).
Therefore, 0.2 moles of CH4 will contain (0.2 moles) * (4 moles C−H bonds/mole of CH4) = 0.8 moles of C−H bonds.
Next, we multiply the number of moles of C−H bonds by the bond energy of each C−H bond:
Total energy = (0.8 moles C−H bonds) * (393 kJ/mole C−H bond) = 314.4 kJ
Therefore, it would require 314.4 kJ of energy to break all the simple bonds in 0.2 moles of CH4.
b) Now let's estimate the energy released in the reaction:
CO (g) + 2 H2 (g) → CH3OH
First, let's break down the bonds in the reactants:
- In CO, we have one C≡O bond with a bond energy of 1075 kJ.
- In H2, we have two H−H bonds with a bond energy of 435 kJ each.
Next, let's calculate the total energy required to break the bonds in the reactants:
Energy required = (1 C≡O bond) * (1075 kJ/C≡O bond) + (2 H−H bonds) * (435 kJ/H−H bond)
= 1075 kJ + 2 * 435 kJ
= 1945 kJ
Now, let's look at the product CH3OH:
- In CH3OH, we have three C−H bonds with a bond energy of 393 kJ each, and one C−O bond with a bond energy of 356 kJ.
Next, let's calculate the total energy released when forming the new bonds in the product:
Energy released = (3 C−H bonds) * (393 kJ/C−H bond) + (1 C−O bond) * (356 kJ/C−O bond)
= 3 * 393 kJ + 356 kJ
= 1525 kJ
Finally, we calculate the net energy change in the reaction:
Net energy change = Energy released - Energy required
= 1525 kJ - 1945 kJ
= -420 kJ
In the reaction CO (g) + 2 H2 (g) → CH3OH, the estimated energy released is -420 kJ. The negative sign indicates that the reaction is exothermic, meaning it releases energy.