MediumChemistryHigh School (11–12)Organic Compounds with Functional GroupsNumerical

The conjugate acid of the hydrogencarbonate ion is carbonic acid, with a pKa of 6.35…

Try it on paper first. A hint, the key idea and the worked solution are here when you need them.

The conjugate acid of the hydrogencarbonate ion is carbonic acid, with a pKa of $6.35$ . For the reaction of an acid HA with hydrogencarbonate, $K = 10^{\,6.35 - pK_a(\text{HA})}$ . Find $\log_{10} K$ for phenol ( $pK_a = 10.0$ ), $K$ for p-nitrophenol ( $pK_a = 7.2$ ) and $\log_{10} K$ for picric acid ( $pK_a = 0.4$ ). Say which of the three would release carbon dioxide from the solid salt.

Need a reminder? The key ideaShow

For a weak acid HA, $K_a = 10^{-pK_a}$ and $[\text{H}^+] = \sqrt{K_a c}$ . For HA with a base B $^-$ : $K = 10^{\,pK_a(\text{HB}) - pK_a(\text{HA})}$ . The share of HA present as the anion is $\dfrac{100}{1 + 10^{\,pK_a - \text{pH}}}$ percent.

The worked solution

Have you tried it?

Work it out on paper first. It is fine to get stuck or make a mistake: that is how we learn. When you are ready, go through the solution one step at a time, and check each step against your own.

← All Problems

← Phenol has a pKa of 10.0. A solution is made by dissolving 0.050 mol of phenol in water to make 1.0…A chemist studies the anion share of two phenols at two pH values… →

More onOrganic Compounds with Functional Groups

Discussion (0)

Loading…