A buffer that contains 0.578 M base, B, and 0.263 M of its conjugate acid, BH , has a pH of 8.97. What is the pH after 0.0020 mol of HCl is added to 0.250 L of this solution?

pH = 8.95

Explanation:

A buffer follows H-H equation:

pH = pKa + log [B] / [BH⁺]

Where pH is pH of the buffer: 8.97

pKa is a constant of the buffer (Our incognite)

[B] is molar concentration -or moles- of the base: 0.578M

[BH⁺] is molar concentration -or moles- of conjugate acid: 0.263M

pH = pKa + log [B] / [BH⁺]

8.97 = pKa + log [0.578M] / [0.263M]

8.628 = pKa of the buffer

0.250L contains:

[B] = 0.578M * 0.250L = 0.1445 moles of B

[BH⁺] = 0.263M * 0.250L = 0.06575 moles of BH⁺

When HCl is added, B is consumed and BH⁺ is produced as follows:

HCl + B → BH⁺ + Cl⁻

That means moles of each species after the addition of HCl is:

[B] = 0.1445 moles - 0.0020moles = 0.1425moles

[BH⁺] = 0.06575 moles + 0.0020moles = 0.06775moles

Replacing in H-H equation, pH is:

pH = 8.628 + log [0.1425moles] / [0.06775moles]

2h2o2--> 2h2o + o2

this reaction is of the spontaneous decomposition of hydrogen peroxide down into water and oxygen.

add 2 molecules of hydrogen peroxide and 2 molecules of water. since oxygen is naturally diatomic, the total number of atoms of each element is now the same on both sides of the equation so it is balanced.

this may not be entirely correct but let me know.