(a) Will Co(OH)2 precipitate from solution if the pH of a 0.020 M solution of Co(NO3)2 is adjust

step 1 We have two calculations to do for this problem. First, we are asked if cobalt 2 hydroxide will

(a) Will Co(OH)2 precipitate from solution if the pH of a...

(a) Will $\mathrm{Co}(\mathrm{OH})_{2}$ precipitate from solution if the $\mathrm{pH}$ of a $0.020 \mathrm{M}$ solution of $\mathrm{Co}\left(\mathrm{NO}_{3}\right)_{2}$ is adjusted to $8.5 ?(\mathbf{b})$ Will $\mathrm{AgIO}_{3}$ precipitate when $20 \mathrm{~mL}$ of $0.010 \mathrm{M} \mathrm{AgIO}_{3}$ is mixed with $10 \mathrm{~mL}$ of $0.015 \mathrm{M} \mathrm{NaIO}_{3} ?\left(K_{s p}\right.$ of $\mathrm{AgIO}_{3}$ is $3.1 \times 10^{-8} .$ )

Key Concepts

Solubility Product Constant (Ksp)

The solubility product constant is the equilibrium constant for the dissolution of a sparingly soluble salt. It is defined as the product of the concentrations of the ions raised to their stoichiometric coefficients. Its value determines whether or not a precipitate will form in a solution when the product of the ion concentrations exceeds the Ksp value.

Ion Product (Q) and Its Comparison to Ksp

The ion product is calculated by multiplying the current concentrations of the ions in solution, raised to their stoichiometric coefficients. By comparing Q to the Ksp, one can predict precipitation: if Q exceeds Ksp the salt will precipitate, if Q is less than Ksp no precipitation occurs, and if Q equals Ksp the solution is saturated.

Effect of pH on Solubility

pH impacts the solubility of compounds, especially those forming basic or acidic ions such as hydroxides. In solutions where the hydroxide ion concentration is significant, changes in pH can shift the equilibrium and affect whether a metal hydroxide will remain dissolved or precipitate.

Dilution and Mixing of Solutions

When two solutions are combined, the final volume increases leading to changes in the concentrations of the dissolved species. This dilution effect must be considered when calculating ion concentrations and assessing whether the resulting ion product will exceed the Ksp threshold, resulting in precipitation.

Transcript

00:01 We have two calculations to do for this problem.

00:04 First, we are asked if cobalt 2 hydroxide will precipitate from solution if the ph is adjusted of a solution is adjusted to 8 .5.

00:14 Here's our first substance, and i'm going to write down the information for first calculation.

00:27 I'll abbreviate precipitate ppp.

01:06 Okay, so here's everything for our first problem.

01:09 Again, will the cobalt 2 hydroxide precipitate from solution? if the ph of a 0 .020 molar solution is adjusted to 8 .5.

01:23 Okay, in order to do this, i like to always write down my chemical equation.

01:49 And if we look our ksp up for this, it is 1 .3 times 10 to the minus 15th.

01:59 I'm going to write that somewhere else.

02:13 I often write my o's too big for cobalt.

02:30 When i looked up the ksp, again, it is 1 .3.

02:38 Times 10 to the minus 15th.

02:47 There's the ksp.

02:49 Now, let's figure out, let's get ready to calculate q, and q is going to be equal to our actual concentrations, and our cobalt, let me write these over here, our cobalt concentration was given as 0 .020 molar, and a hydroxide concentration, we will figure out by using our ph.

03:26 So 14 minus 8 .5 equals 5 .5 for my p .o .h.

03:34 And if i take 10 to the negative 5 .5, 10 to the 9, i get 3 .16 times 10 to the minus 6.

03:48 So then i'm going to multiply this by 3 .16 times 10 to the minus 6.

03:54 And we're going to square that.

03:56 Don't forget that we have to square that one.

04:00 And that this equals 2 times 10 to the minus 6th.

04:07 So the two values we need to compare our q is 2 times 10 to the minus 13th and our ksp 1 .3 times 10 to the minus 15th.

04:27 So q is greater than ksp which means that the cobalt hydroxide, cobalt 2 hydroxide, will precipitate.

04:46 And i think that's everything i need to do for that problem.

04:49 Next we have our ag i -o -3.

04:57 And for this we're given two solutions.

05:01 Our solutions are 20 milliliters of 0 .010 molar silver nitrate and 10 milliliters of 0 .015 molar sodium iodate...

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