Calculate the volume, in milliliters, of a 0.470 M KOH solution that should be added to 5.250 g of HEPES (MW = 238.306 g/mol, pKa = 7.56) to give a p

17.13mL

Explanation:

Complete question:

to give a pH of 7.32.

Hepes is a weak acid. When HEPES reacts with KOH its conjugate base, HEPES⁻ is produced:

HEPES + KOH → HEPES⁻

Now when you have in solution both the weak acid and conjugate base a buffer is produced. The equation that relates pKa and pH of a buffer is H-H equation:

pH = pKa + log [HEPES⁻] / [HEPES]

Where [] could be taken as the moles of each specie.

Replacing:

7.32 = 7.56 + log [HEPES⁻] / [HEPES]

-0.24 = log [HEPES⁻] / [HEPES]

0.57544 =  [HEPES⁻] / [HEPES] (1)

Now, moles of 5.250g of HEPES is:

Mass HEPES:

5.250g * (1mol / 238.306g) = 0.02203 moles HEPES.

That means:

0.02203 moles = [HEPES⁻] + [HEPES] (2)

Replacing (2) in (1):

0.57544 =  0.02203 moles - [HEPES] / [HEPES]

0.57544[HEPES] =  0.02203 moles - [HEPES]

1.57544[HEPES] = 0.02203 moles

[HEPES] = 0.01398 moles HEPES.

And [HEPES⁻] = 0.02203 moles - 0.01398 moles =

0.00805 moles of HEPES⁻

As HEPES⁻ is produced from HEPES and KOH, if we add 0.0805 moles of KOH, we will have in solution 0.00805 moles of HEPES⁻ and 0.01398 moles of HEPES.

To obtain 0.00805 moles of KOH from a 0.470M KOH, you need to add:

0.00805 moles KOH * (1L / 0.470mol) = 0.01713L of 0.470M KOH =

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.