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ikadub [295]
3 years ago
11

If a weak acid is 25% deprotonated at ph 4, what is the pka?if a weak acid is 25% deprotonated at ph 4, what is the pka?

Chemistry
2 answers:
Oksanka [162]3 years ago
7 0
4.48
pH=pKa+log([A-/HA])

25% deprotonated tells us that A- is .25 and that the rest (75% is protonated) thats .75.

4 = pKa + log\frac{.25}{.75}
4 - log\frac{.25}{.75} = pKa
4.48=pKa

nikitadnepr [17]3 years ago
4 0

Answer:

pKa = 4.5

Explanation:

The weak acid can be represented by the general formula, HA and the dissociation equilibrium given as:

HA \rightleftharpoons H^{+}+A^{-}

where HA = protonated form

A- = deprotonated form

The Henderson-Hasselbalch equation relates the pH of a solution to the ratio of the concentrations of HA and A- as;

pH = pKa + log\frac{[A-]]}{[HA]]}-----(1)

It is given that:

% deprotonated i.e. A- = 25%

Therefore, %protonated i.e. HA = 100 -25 = 75%

pH = 4

Based on equation (1)

4 = pKa + log\frac{[25]]}{[75]]} = pKa-0.477

pKa = 4.477 i.e. around 4.5

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Answer:

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LEARNING OBJECTIVES

Describe the structure and function of the enteric nervous system (ENS)

KEY TAKEAWAYS

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The ENS consists of two plexuses, the submucosal and the myenteric. The myenteric plexus increases the tone of the gut and the velocity and intensity of contractions. The submucosal plexus is involved with local conditions and controls local secretion, absorption, and muscle movements.

While described as a second brain, the enteric nervous system normally communicates with the central nervous system (CNS) through the parasympathetic (via the vagus nerve ) and sympathetic (via the prevertebral ganglia) nervous systems, but can still function when the vagus nerve is severed.

The ENS includes efferent neurons, afferent neurons, and interneurons, all of which make the ENS capable of carrying reflexes and acting as an integrating center in the absence of CNS input.

The ENS contains support cells, which are similar to the astroglia of the brain, and a diffusion barrier around the capillaries surrounding the ganglia, which is similar to the blood –brain barrier of cerebral blood vessels.

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The second brain of the enteric nervous system is the reason we get butterflies in our stomach or need to use the restroom more frequently when we are nervous and/or under stress.

The gastrointestinal (GI) system has its own nervous system, the enteric nervous system (ENS). Neurogastroenterology is the study of the enteric nervous system, a subdivision of the autonomic nervous system (ANS) that directly controls the gastrointestinal system. The ENS is capable of autonomous functions such as the coordination of reflexes.

Although it receives considerable innervation from the autonomic nervous system, it can and does operate independently of the brain and the spinal cord. The ENS consists of some 100 million neurons, one-thousandth of the number of neurons in the brain, and about one-tenth the number of neurons in the spinal cord. The enteric nervous system is embedded in the lining of the gastrointestinal system.

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