White vinegar is a 5.0% by mass solution of acetic acid in water. If the density of white vinega

White vinegar is a 5.0% by mass solution of acetic acid in...

Key Concepts

Percent by Mass Solution

A percent by mass solution indicates the mass of solute present in a given mass of solution expressed as a percentage. It is a key concept for determining the amount of an active chemical species in a solution, and is used to relate a known volume or mass of the solution to the mass of the solute present, enabling subsequent conversions to moles or molarity.

Density and Molarity Conversion

Density connects the mass of a solution to its volume, allowing for the conversion between mass-based concentration units and molarity. By knowing the density of the solution, one can calculate the total mass per unit volume and, given a percent by mass concentration of the solute, determine the molar concentration (moles per liter) which is essential for equilibrium calculations.

Weak Acid Equilibrium

Weak acids like acetic acid only partially dissociate in solution. The acid dissociation constant (Ka) quantifies the extent of this ionization. Understanding the equilibrium between the undissociated acid and its dissociation products is crucial for calculating the concentration of hydrogen ions in solution using an equilibrium expression.

pH Calculation

pH is a measure of the acidity of a solution, defined as the negative logarithm of the hydrogen ion concentration. In the context of a weak acid solution, pH calculation typically involves determining the molar concentration of the acid, applying the acid dissociation equilibrium to find the concentration of hydrogen ions, and computing pH using its definition.

Transcript

00:01 Problem 71 from chapter 14 is asking us to calculate the ph of a solution that's 5 % acetic acid in water.

00:11 We are given the information that the density of white vinegar is 1 .007 grams per cubic centimeter.

00:20 So this is a multi -part question, but the first thing we need to determine is a molarity of the acetic acids so that we can go ahead and do our, table so given that the density of acetic acid is equal to 1 .007 grams per per cubic centimeter which is the same as actually saying 1 .007 grams per mil we then want to determine the amount of grams in the solution so the way that we do that is we remember that mass is equal to the density times of volume of a solution.

01:12 And that way, what we can do is we do grams per mill, we multiply that by one liter, and then the conversion rate between two liters and liters.

01:30 And then that gives us our answer in grams, which is going to be 1 ,0007 grams of the solution.

01:39 So making sure our units cancel here, milliliters, milliliters, a liter at liter.

01:44 More left with grinks.

01:45 That's great.

01:47 The next part of the question is then taking into consideration that their solution is 5 % of acetic acid.

01:55 So what we need to do is multiply this to get by 5 % to get our mass of acetic acid.

02:06 And that is equal to acetic acid is equal to 50 .35 grams.

02:21 Next we need to calculate the moles.

02:24 So we must incorporate the molecular weight of acetic acid, which is 60 .05 grams per moles.

02:36 So all we do is take this 50 .35 grams, divided by the molecular weight of acetic acid in grams per mole, which is 60 .05, and our gram the canceling ounce, so we're left with moles, and what we are left with 0 .84 moles.

02:59 However, because we are looking at a solution, we want to answer in malarity, we must multiply by one liter to our answer in malaria.

03:12 So then that leaves us with 0 .8 for valerity, acetic acid.

03:20 So now we can actually go ahead and write our equation and then we can fill out our ice table.

03:32 So this is acetic acid and in water.

03:58 And on the other side of the equation we have hydronium and acetic acid with a proton that has been donated.

04:18 Oops, that's a c.

04:22 C o, o minus.

04:26 Okay, so let's go ahead and do our ice table.

04:31 So from the previous part of the question, we determined that the initial concentration of acetic acid is right here, so it is 0 .8.

04:42 4 moles per liter.

04:46 So we'll go ahead and write that in here...

Please give Ace some feedback