If your answer is 64.5 x 104, what must you do to report in scientific notation?

6.45 x 10^5

In scientific notation, the coefficient must be between 1 and 10.

To convert a number in which the coefficient is greater than 10, you

1.Move the decimal point enough places to the left to make the coefficient between 1 and 10

2.Increase the exponent by the number of places you moved the decimal point

In the coefficient 64.5, you must move the decimal point one place to the left to get 6.45 (a number between 1 and 10), so you increase the exponent by one.

Thus, 64.5 x 10^4 = 6.45 x 10^5

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.