Pentaborane−9 (b5h9) is a colorless, highly reactive liquid that will burst into flames when exposed to oxygen. the reaction is 2b5h9(l) + 12o2(g) → 5b2o3(s) + 9h2o(l) calculate the kilojoules of heat released per gram of the compound reacted with oxygen. the standard enthalpy of formations of b5h9(l), b2o3(s), and h2o(l) are 73.2, −1271.94, and −285.83 kj/mol, respectively.

Answer : The heat released per gram of the compound reacted with oxygen is 71.915 kJ/g

Explanation :

Enthalpy change : It is defined as the difference in enthalpies of all the product and the reactants each multiplied with their respective number of moles. It is represented as

The equation used to calculate enthalpy change is of a reaction is:  

The equilibrium reaction follows:

The equation for the enthalpy change of the above reaction is:

We are given:

Putting values in above equation, we get:

Now we have to calculate the heat released per gram of the compound reacted with oxygen.

From the reaction we conclude that,

As, 2 moles of compound released heat = -9078.57 kJ

So, 1 moles of compound released heat =

For per gram of compound:

Molar mass of = 63.12 g/mole

Therefore, the heat released per gram of the compound reacted with oxygen is 71.915 kJ/g

catya that's not even a b or c

hydrocarbons are organic compounds that contain only hydrogens and carbons. they can be saturated (those which contain only carbon-carbon single bonds) or unsaturated (those which contain carbon-carbon double or triple bonds) in nature. hydrocarbons can undergo several reactions like substitution, elimination etc.  

on substituting one or more hydrogen atoms in hydrocarbon it results in the formation of haloalkane. as the halogen atoms are large compared to the carbon and hydrogen atoms, due to which the molecular weight increases and the bond become polar because of presence electronegative halogen atom and results in the increase in boiling point of the haloalkane.

thus, the correct option is (b) that is the boiling point of the new compound increases on substituting a hydrogen atom with a halogen in a hydrocarbon.