What is the (a) [H+], (b) [OH-], (c) pH, and (d) pOH of a 0.002 M solution of HNO3?
To determine the values of (a) [H+], (b) [OH-], (c) pH, and (d) pOH of a 0.002 M solution of HNO3, we can use some basic concepts in chemistry.
(a) [H+]:
HNO3 is a strong acid, meaning it fully dissociates in water to produce H+ ions and NO3- ions. Since the concentration of HNO3 is 0.002 M, the concentration of H+ ions is also 0.002 M.
(b) [OH-]:
In water, H+ ions and OH- ions are present as a result of the self-ionization of water. However, in this case, because HNO3 is a strong acid, it completely reacts with water, leaving no OH- ions in the solution. Therefore, the concentration of OH- ions is zero.
(c) pH:
The pH of a solution can be calculated using the equation pH = -log[H+]. Substituting the concentration of H+ ions (0.002 M) into the equation gives:
pH = -log(0.002)
pH ≈ 2.70
(d) pOH:
The pOH of a solution can be calculated using the equation pOH = -log[OH-]. Since the concentration of OH- ions is zero, the pOH of this solution is undefined.
Therefore, the answers are:
(a) [H+]: 0.002 M
(b) [OH-]: 0 M
(c) pH: 2.70
(d) pOH: undefined
To find the (a) [H+], (b) [OH-], (c) pH, and (d) pOH of a 0.002 M solution of HNO3, we need to understand the properties of the acid and its dissociation in water.
HNO3 is a strong acid, which means it will dissociate completely in water, producing H+ ions and the conjugate base NO3-.
(a) [H+]:
Since HNO3 is a strong acid and will dissociate completely, the concentration of [H+] in the solution will be equal to the initial concentration of the acid. Therefore, [H+] = 0.002 M.
(b) [OH-]:
To find the concentration of the hydroxide ions, [OH-], we need to consider water autoprotolysis. Water molecules can act as both acids and bases, forming H+ and OH-. In pure water, the concentration of [H+] and [OH-] is 10^-7 M. However, in an acidic solution like HNO3, the concentration of [OH-] will be very small since it is consumed by the reaction with H+.
(c) pH:
The pH is a logarithmic scale that measures the acidity or basicity of a solution. It is calculated using the formula: pH = -log[H+].
In this case, the concentration of [H+] is 0.002 M, so we can calculate the pH using the equation: pH = -log(0.002).
Using a logarithm calculator or math software, we find that the pH is approximately 2.70.
(d) pOH:
The pOH is another logarithmic scale that represents the concentration of OH- ions in a solution. It is calculated using the formula: pOH = -log[OH-].
Since we know that [OH-] is small and insignificant in an acidic solution like HNO3, we can assume that the pOH is close to 7 (the pOH of pure water).