A student dissolves 0.0100 mole of an unknown weak base in 100.00 mL water and titrates the
solution with 0.100 MHNO3. After 40.00 mL of 0.100M HNO3 was added, the pH of the resulting solution was 8.00. Calculate Kb
value for the weak base.

The value of for weak base is

Explanation:

We are given:

Moles of unknown weak base = 0.0100 moles

To calculate the number of moles for given molarity, we use the equation:

Molarity of nitric acid = 0.100 M

Volume of solution = 40.0 mL

Putting values in above equation, we get:

The chemical reaction for unknown weak base (BOH) and nitric acid follows the equation:

Initial:          0.0100       0.004        

Final:           0.006          -             0.004

Volume of solution = 100 + 40 = 140 mL = 0.140 L    (Conversion factor:  1 L = 1000 mL)

To calculate the pOH of basic buffer, we use the equation given by Henderson Hasselbalch:

We are given:

= negative logarithm of acid dissociation constant of formic acid = ?

pH = 8.00

pOH = 14 - pH = 14 - 8 = 6

Putting values in above equation, we get:

We know that:

Hence, the value of for weak base is

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.