The equation below represents the combination of gaseous atoms of non-metal X and of hydrogen to form gaseous X2He6 molecules. 2X(g) + 6H(g) → X2H6(g) AH = -2775 kJ mol The bond energy of an X-H bond is 395 kJ mol. What is the bond energy of an X-X bond? A - 405.0kJmol-¹ B -202.5kJmol-¹ C +202.5kJ mol-¹ D +405.0kJ mol-¹

D +405.0kJ mol-¹

Explanation:

Since bond energy is the energy required to break a bond, the energy of dissociation of X₂H₆ = +2775 kJmol⁻¹.

Since there is one X-X bond and six X-H bonds,

Bond energy of one X-X bond + Bond energy of six X-H bonds = energy of dissociation of X₂H₆.

Since bond energy of one X-H bond = 395 kJ mol⁻¹, then

Bond energy of one X-X bond + Bond energy of six X-H bonds = energy of dissociation of X₂H₆

Bond energy of one X-X bond + 6 × one X-H bond = +2775 kJmol⁻¹.

Bond energy of one X-X bond + 6 × 395 kJ mol⁻¹ = +2775 kJmol⁻¹.

Bond energy of one X-X bond + 2370 kJ mol⁻¹ = 2775 kJmol⁻¹

Bond energy of one X-X bond = 2775 kJmol⁻¹ - 2370 kJ mol⁻¹

Bond energy of one X-X bond = +405 kJmol⁻¹

2fe + 3h2so4 -> fe2(so4)3 + 3h2

it is necessary to balance equations in order to get the proper amount of reactants as well as products in order not to make a miscalculation.

you cannot change the subscripts as that would change the substance itself. for instance, diatomic elements such as h2 only have the subscript two when a gas. another example would be so4, if you were to change the subscript, the element would no longer be sulfate.

we change the coefficients instead as that only changes the number of molecules rather than the substance itself.

hope this !