Suppose that you have 125 mL of a buffer that is 0.140 M in both hydrofluoric acid ( HF ) and its conjugate base ( F − ) . Calculate the maximum volume of 0.370 M HCl that can be added to the buffer before its buffering capacity is lost.

38,7mL of HCl 0,370M

Explanation:

The buffering capacity is lost when the pH of the solution is out of pka ± 1.

For the buffer:

HF ⇄ H⁺ + F⁻; pka = 3,20

Moles of both HF and F⁻ are:

HF: 0,140M ₓ 0,125L = 0,0175 moles of HF

Moles of F⁻ are the same.

Using Henderson-Hasselbalch formula:

pH = pka + log₁₀ F⁻ / HF

pH = 3,20 + log F⁻ / HF (1)

The addition of X moles of HCl (H⁺) shift the equilibrium to the left, thus:

         HF             ⇄   H⁺  +     F⁻

0,0175 moles + X             0,0175 moles - X          

The buffer lost its capacity when pH = 3,20 - 1 = 2,20. Thus, replacing in (1):

2,20 = 3,20 + log ₁₀0,0175 - X / 0,0175 + X

0,1 = 0,0175 - X / 0,0175 + X

0,00175 + 0,1X = 0,0175 - X

-0,01575 = -1,1X

0,0143 moles = X

You need to add 0,0143 moles of HCl. In volume for a concentration of 0,370M HCl:

0,0143 moles ÷ 0,370M = 0,0387L of HCl 0,370M ≡ 38,7mL of HCl 0,370M

I hope it helps!

explanation:

venn diagram is pictorial representation with of circles showing the relation between two finite sets or things. the intersection part of two circles conveys the relation present in between those sets or things.

here in the venn diagram of sand and salt two circles represent sand and salt. but the area falling under the intersection of these circle represents the mixture of sand and salt.

so, in a venn diagram the mixture will be placed in a middle that is in between the intersection of two circles.

answer: -

reaction:

na + cl ⇌ nacl

balanced chemical equation:

na + 2cl ⇌ nacl2

sodium + clorine goes to form sodium chloride (table salt).

the product is nacl2.

and the reactants are na and cl.

(note: if you don’t know what ⇌ means, read below: -

⇌(double head arrow) means reversible reaction).