What is the pH of a solution containing 0.8 M morphine and 0.025 M morphine sulfate solution in

step 1 is a weak base. A .15 molar solution of morphine has a pH of 10 .7. What is the KB for morphine?

What is the pH of a solution containing 0.8 M morphine and...

Key Concepts

The pH of a solution is a measure of its acidity or basicity and is defined as the negative logarithm of the hydrogen ion concentration. It provides a scale—from acidic to basic—that indicates the relative balance of H+ ions in the solution.

pKa

The pKa is a constant that represents the acid dissociation equilibrium of a molecule. It is the pH at which half of the species are deprotonated, serving as a pivotal point in understanding a compound's strength as an acid or base in a solution.

Henderson-Hasselbalch Equation

This equation relates the pH of a buffer solution to its pKa and the ratio of the concentrations of the conjugate base to the acid. It is a useful tool for estimating the pH of solutions that contain a mixture of a weak acid and its conjugate base or a weak base and its conjugate acid.

Acid-Base Equilibrium

Acid-base equilibrium concerns the reversible reaction between acids and bases in solution, determining the proportions of ionized and non-ionized forms. This equilibrium is essential for predicting how mixing compounds with acidic and basic properties will influence the overall pH.

Buffer Systems

Buffer systems are solutions that resist changes in pH upon the addition of small amounts of acids or bases. They typically consist of a weak acid and its conjugate base (or a weak base and its conjugate acid) and maintain the pH within a narrow range, making them crucial in many chemical and biological applications.

Transcript

00:01 Is a weak base.

00:02 A .15 molar solution of morphine has a ph of 10 .7.

00:08 What is the kb for morphine? so to start this problem, we've got to consider that we're given a weak base.

00:19 So, a solution of a weak base.

00:23 I have that substance in water, and we're going to denote it as b, instead of figuring out the formula of morphine.

00:32 We're just going to denote it as b.

00:34 So we have our base, and we have that in water.

00:41 So being a weak base, it's going to accept a proton.

00:47 So it's going to take a proton from the water molecule.

00:53 So that's going to create bh plus, a protonated base molecule.

01:00 And that will leave behind hydroxide ion from the water molecule.

01:06 Now, you should notice that when i wrote this reaction, i used an equilibrium arrow instead of an arrow pointing forward only.

01:15 Because this is a weak base.

01:18 A weak base only partially accepts protons.

01:21 So only a small fraction of those base molecules in solution except a proton.

01:27 The majority actually remain neutral.

01:30 So this equilibrium reaction, just like any other equilibrium reaction, has an equilibrium constant associated with it.

01:40 And that equilibrium constant is denoted as kb, since it's a base, or a base actually ionizing.

01:49 So we have kb, and we can write the equation that goes with that.

01:54 Kb would be equal to our product concentrations over our reactant concentrations.

02:00 So, b .h.

02:03 Plus times the concentration of hydroxide ion.

02:10 That's our products.

02:13 And then that would all be over the concentration of our base.

02:19 Now, notice, i've left water out of that k equation because water is pure liquid.

02:27 Its concentration does not change.

02:29 And so that doesn't go in the k equation.

02:33 Just like any other equilibrium constant expression.

02:37 So this is what the question is actually asking for us to figure out.

02:42 The kb value, that's what it wants to know.

02:46 And so that means we need concentrations to plug into this equation.

02:52 So let's look at what information we're given.

02:56 We're given that we have a 0 .15 molar solution of morphine, and we're told the ph of that.

03:04 Solution.

03:06 And since this is an equilibrium reaction, we're going to go ahead and set up what we call an ice table, something that shows us our initial amounts, our change in those amounts as it goes towards equilibrium and then our equilibrium amounts.

03:25 So i've got my three rows.

03:29 And in this, i've got my initial row, my change, and my equilibrium.

03:38 So i'm going to fill in information that was given.

03:42 Now, in this table, another good thing to realize is, since water's not in that equilibrium expression, i can also go ahead and eliminate it from the table.

03:56 I don't need to worry about how much water there is.

04:01 Now, that 0 .15 molar that we were given, that is how we prepare this solution.

04:09 So that's really the start amount.

04:12 That's how much base we put in.

04:15 And so that is the 0 .150 molar.

04:21 Now, to start with, we only put that neutral base in solution.

04:26 So there was no bh plus.

04:28 So i'm going to cross that end.

04:29 Now, the oh minus, i'm also going to say starts at zero.

04:35 Although it actually, in water, it's got a concentration of 10 to the negative 7th molar, but that should be negligible with respect to how much gets produced because of this base.

04:49 And we can go back and look at that.

04:51 So now comes the ph...

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