Ascientist observes that after mixing a solid powder into water, the ph of the newly formed solution is 2.7. what can he infer from this observation?
the solution contains an indicator that has a ph of 2.7.
the solid powder contained hydrogen ions.
the ph indicator was used incorrectly.
the powder increased the hydrogen ion concentration of the solution.

The correct answer is
The powder increased the hydrogen ion concentration of the solution.

This means that the powder turned water into a more acidic substance since water's pH factor is 7, and things under 7 are acids.

What are the choices?

Answerthis solution will not form a precipitateexplanationsolubility equilbrium:         pbf₂(s)  ⇄ pb²⁺(aq) + 2 f⁻(aq)the solubility product expression is    (we exclude solids from the equilibrium expression).now suppose we have the trial ion product q, which we can define as    then, we can interpret  q as the product of the concentration of the ions that we have and ksp as the product of the ion concentrations that are needed to form a saturated solution.if q > ksp, then that implies that there will be a surplus of ions that exceed the amount that is required to form a saturated solution. a precipitate will then form (the precipitate continually  forms until the surplus ions are removed and q is decreased to ksp's value).if q = ksp, the saturated solution that forms is barely saturated and the precipitate will be minimal.if q < ksp, then the ion concentration will not be enough to form a saturated solution (so no precipitate).using our information, we calculate the trial ion product:     since q = 2.7  × 10⁻⁸ < ksp =  4  ×  10⁻⁸, a precipitate will not form.