Why are groups 1 and 2 referred to as the s-block of the periodic table

This is because their valence electrons are located in the S - orbital

Explanation:

This is because their valence electrons are located in the S - orbital.

The answer to your question is pH = 2.28

Explanation:

Chemical reaction

                    HCOOH(ac)  +  H₂O  ⇔   H₃O⁺   +  HCOO⁻

I                        0.15                 --              0               0

C                       - x                   --             +x              +x

F                     0.15 - x             --               x                x

Write the equation of equilibrium

Substitution

But     0.15 - x ≈   0.15

Solve for x

                             x² = (0.15)(1.8 x 10⁻⁴)

Simplification

                             x² = 0.000027

Result

                             x = 0.0052

                          pH = -log [H₃O⁺]

Substitution

                          pH = - log [0.0052]

Simplification and result

                         pH = 2.28