What simplifying assumptions do we usually make in working problems involving equilibria of salts of polyprotic acids? Why are they usually valid? Answer by selecting all true statements.
Are the answers: a,b,d,and f
A)If the two ionization constants are not very different the approximations are valid.
B)The concentration of OH- and the conjugate acid of the weak base (the anion of the salt) are approximately equal.
C)Nearly all of the OH- comes from the first ionization.
D)Nearly all of the OH- comes from the second ionization.
E)The approximations are usually valid because the first ionization constant is usually much larger than the second ionization constant.
F)The approximations are usually valid because the first ionization constant is usually smaller than the second ionization constant.
c) Nearly all of the OH- comes from the first ionization.
e) The approximations are usually valid because the first ionization constant is usually much larger than the second ionization constant.
b) The concentration of OH- and the conjugate acid of the weak base (the anion of the salt) are approximately equal.
The correct answers are A), B), D), and F).
A) If the two ionization constants are not very different, the approximations are valid. This means that if the difference between the two ionization constants is small, the simplifying assumptions made in working problems involving equilibria of salts of polyprotic acids can be considered valid.
B) The concentration of OH- and the conjugate acid of the weak base (the anion of the salt) are approximately equal. This assumption is usually valid because the equilibrium concentrations of the weak base and its conjugate acid are similar at equilibrium.
D) Nearly all of the OH- comes from the second ionization. This assumption is usually valid because the first ionization of a polyprotic acid typically produces a much larger concentration of the conjugate acid compared to the second ionization, resulting in a higher concentration of OH- from the second ionization.
F) The approximations are usually valid because the first ionization constant is usually smaller than the second ionization constant. This is generally true for polyprotic acids, where the second ionization constant is often larger than the first ionization constant.
The correct answers are A, B, D, and F.
To solve problems involving equilibria of salts of polyprotic acids, we often make simplifying assumptions. These assumptions are usually valid under certain conditions.
A) If the two ionization constants of the polyprotic acid are not very different, the approximations are valid. This means that the acid does not significantly ionize in multiple steps.
B) The concentration of hydroxide ions (OH-) and the conjugate acid of the weak base (the anion of the salt) are approximately equal. This assumption is valid when the reaction reaches equilibrium.
C) The assumption that nearly all of the hydroxide ions come from the first ionization is not always valid. In some cases, significant hydroxide ions can come from the second ionization or subsequent ionizations.
D) The assumption that nearly all of the hydroxide ions come from the second ionization is valid in cases where the acid predominantly ionizes in the second step.
E) This statement is not necessarily true as the validity of the approximations does not solely depend on the relative magnitudes of the first and second ionization constants.
F) The approximations are usually valid because the first ionization constant is usually smaller than the second ionization constant. This is often the case for polyprotic acids where subsequent ionizations require the removal of additional protons from already ionized species, making them less favorable.
A is not true. You would LIKE about 10^5 difference in k1 and k2 but usually we can live with 10^3(1000 times) and in some cases even 10^2 (100 time) but never as close as 10^1 (10 times)
I don't believe B is true but the statement isn't really all that clear to me.
C is not true.
D is true if we're talking diprotic acids. Probably not true true for triprotic acids.
E is generally true.
F is not true. k2 is ALWAYS smaller than k1.