A 100.0 mL sample of 0.18 M HCl is titrated with 0.27 M KOH at 25°C. Determine the pH of the solution after the addition of 66.67 mL of the KOH titrant.

pH = 7.0

Explanation:

The HCl reaction with KOH as follows:

HCl + KOH → H₂O + KCl

To find pH first we need to know how many moles of each reactant reacts as follows:

HCl = 0.1000L * (0.18 mol / L) = 0.018 moles HCl

KOH = 0.06667L * (0.27mol / L) = 0.018 moles KOH

That means all HCl reacts with all KOH and you will have in solution just water. The equilibrium of water is:

H₂O(l) ⇆ H⁺(aq) + OH⁻(aq)

K = 1x10⁻¹⁴ = [H⁺] [OH⁻]

As the amount of H⁺ = OH⁻:

1x10⁻¹⁴ = [H⁺]²

[H⁺] = 1x10⁻⁷M

as pH = -log [H⁺]

altitude, density, pressure

air gets less dense the higher the altitude and also the air pressure is less as altitude rises.

chemical changes occur when a substance combines with another to form a new substance, called chemical synthesis or, alternatively, chemical decomposition into two or more different substances. these processes are called chemical reactions and, in general, are not reversible except by further chemical reactions. some reactions produce heat and are called exothermic reactions and others may require heat to enable the reaction to occur, which are called endothermic reactions. understanding chemical changes is a major part of the science of chemistry.