The concentration of hydrogen ion in a sample of soft drink is $$3.8 \times 10^{-3} \mathrm{M}$$. What is its $$\mathrm{pH}$$ ?

If the ionic product of $$\mathrm{Ni}(\mathrm{OH})_2$$ is $$1.9 \times 10^{-15}$$, then the molar solubility of $$\mathrm{Ni}(\mathrm{OH})_2$$ in $$1.0 \mathrm{~M} \mathrm{~NaOH}$$ is

100 mL of 2 M of formic acid (pK_a = 3.74) is neutralise by NaOH, at the equivalence point pH is