Question

Phosphoric acid (h3po4) is tribasic, with pka's of 2.14, 6.86, and 12.4. The charge of the ionic form that predominates at ph 3.2 is __________.

Answer 1

Phosphoric acid (H3PO4) is tribasic, with pKa's of 2.14, 6.86, and 12.4. The charge of the ionic form that predominates at pH 3.2 is H2PO4-

Further explanation

Phosphoric acid (H3PO4) is tribasic, with pKa's of 2.14, 6.86, and 12.4. The charge of the ionic form that predominates at pH  3.2 is __________.

• A) H3PO4.
• B) H2PO4-.
• C) HPO42-.
• D) PO43-.
• E) none of the above.

Phosphoric acid, also called orthophosphoric acid, (H3PO4), is the most important oxygen acid of phosphorus. It is used to make phosphate salts for fertilizers. Phosphoric acid also used in dental cements, albumin derivatives, the sugar and textile industries.

A tribasic or triprotic acid is contains three potential protons to donate. Phosphoric acid (H3PO4) is tribasic, with pKa's of 2.14, 6.86, and 12.4.

$H_3PO_4 = H_2PO_4^- + H^+, pKa = 2.14 \\ H_2PO_4^{-} = HPO_4^{2-} + H^+, pKa = 6.86 \\ HPO_4^{2-} = PO_4^{3-} + H^+, pKa = 12.4$

The pKa value is method to indicate the acid strength. It is the negative log of the acid dissociation constant or Ka value. A lower pKa value indicates a stronger acid. Hence the lower value indicates the acid more fully dissociates in water.

The relation between pH and pKa is

$pH = pKa * log \frac{[A^-]}{HA}$

The charge of the ionic form that predominates at pH 3.2 is the pH that close to it which is B) H2PO4- = pH = 6.86

Learn more

1. Learn more about Phosphoric acid brainly.com/question/10722673
2. Learn more about tribasic brainly.com/question/10983988
3. Learn more about the ionic form brainly.com/question/3768883

Answer details

Grade:  9

Subject:  chemistry

Chapter:  biochemistry

Keywords: Phosphoric acid, tribasic, pka, the ionic form, The charge

Answer 2

Correct answer is $H_2PO_4^-$.

Phosphoric acid is a polyprotic acid having 3 acidic hyrdogen therefore it will have 3 pka values.

The equations for the release of acidic hydrogen can be written as:

$\\H_3PO_4\rightleftharpoons H_2PO_4^-+H^+\text{ pka=2.14}\\H_2PO_4^-\rightleftharpoons HPO_4^2^-+H^+\text{ pka=6.86}\\HPO_4^2^-\rightleftharpoons PO_4^3^-+H^+\text{ pka=12.4}$

From the pka values we can judge the idea of pH as using Henderson-Hasselbalch Equation, we get the relation between pH and pka.

$HA\rightarrow H^-+A^-$

Using the following equation, relation of pH and pka is

$pH=pka+log\frac{[A^-]}{HA}$

Using this equation, we can find that the equation having pka= 2. 14 is closest to the pH=3.2 so the ionic form in this equation will be dominant at the same pH.

Therefore at pH=3.2 the ionic form $H_2PO_4^-$ of $H_3PO_4$ is dominant.