Predict whether aqueous solutions of the following...

Predict whether aqueous solutions of the following substances are acidic, basic, or neutral: (a) $\mathrm{CrBr}_{3}$, (b) LiI, (c) $\mathrm{K}_{3} \mathrm{PO}_{4}$, (d) $\left[\mathrm{CH}_{3} \mathrm{NH}_{3}\right] \mathrm{Cl},(\mathrm{e}) \mathrm{KHSO}_{4}$

Key Concepts

Anion Contribution to pH

The anion in a salt influences the pH depending on its origin. Anions derived from strong acids typically do not affect the pH because they do not hydrolyze appreciably, while anions derived from weak acids tend to accept a proton from water, forming the corresponding weak acid and producing hydroxide ions, which can make the solution basic.

Metal Ion Hydrolysis

Metal ion hydrolysis refers to the process where metal cations, especially those with high charge densities such as many transition metals, interact with water molecules. Their strong polarizing power can attract electron density from water, leading to the release of protons and thus an acidic solution. This concept is essential when evaluating salts containing metal cations to determine their impact on pH.

Salt Hydrolysis

Salt hydrolysis is the process by which the ions derived from salts react with water. Depending on the nature of the parent acid and base, this reaction can produce either hydronium or hydroxide ions, resulting in an acidic or basic solution, respectively. Understanding salt hydrolysis is crucial for predicting the pH of a solution when a salt dissolves.

Conjugate Acid-Base Pairs

Conjugate acid-base pairs consist of an acid and the base formed when the acid donates a proton, or vice versa. The relative strengths of these conjugate pairs determine how a salt behaves in solution. For instance, if a salt is derived from a weak acid and a strong base, its anion (the conjugate base) can partially hydrolyze water to yield hydroxide ions, making the solution basic.

Transcript

00:01 In this problem, we were given five different salt solutions and were asked to predict whether they are acidic, basic, or neutral.

00:09 Let's begin.

00:14 Our first substance is chromium -3 bromide.

00:21 And let's look at our cr3 plus and our br -finus.

00:32 So our negatives, this will be a conjugate base of a strong acid so this has no effect.

00:51 And this is conjugate base.

01:00 This is strong acid, and i'll be using sb strong base.

01:09 The cr2 -3 plus is the conjugate acid of a weak base, and this will lower the ph resulting in an acidic solution.

01:57 For b, we are looking.

01:59 Looking at b -l -i -l -i -i -dide.

02:08 This will be a strong one.

02:09 This will be neutral.

02:17 Because the lithium -cadion is the conjugate acid of a strong base, so it'll have no effect, and the iodide ion is the conjugate base of a strong acid, and it will also have no effect.

02:43 So that will be a neutral salt.

02:51 C is potassium phosphate.

03:13 This is a conjugate a conjugate acid of a strong base, thus will have no effect, and this is the conjugate base of a weak acid.

03:32 Therefore, it will raise the ph, and this will be basic...

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