20 mL of an approximately 10% aqueous solution of ethylamine, CH3CH2NH2, is titrated with 0.3000 M aqueous HCl. Which indicator would be most suitable for this titration

20 mL of an approximately 10% aqueous solution of ethylamine, CH3CH2NH2, is titrated with 0.3000 M aqueous HCl. Which indicator would be most suitable for this titration? The pKa of CH3CH2NH3+ is 10.75.

Bromocresol green, color change from pH = 4.0 to  5.6

Explanation:

The equation for the reaction is as follows:

    +          ⇄        

Given that concentration of = 10%

i.e 10 g of in 100 ml solution

molar mass = 45.08 g/mol

number of moles =

= 0.222 mol

Molarity of = 0.222 ×

= 2.22 M

However, number of moles of in 20 mL can be determined as:

number of moles of = 20 mL × 2.22 M

=

Concentration of =

= 2.22 M

Similarly, The pKa Value of  is given as 10.75

pKb value will be: 14 - pKa

= 14 - 10.75

= 3.25

Finally, the pH value at equivalence point is:

pH=

pH =

pH = 5.21

∴

The indicator that is best fit for the given titration is Bromocresol Green Color change from pH between 4.0 to 5.6.

the answer is learned

he would use the colour black