The density of a 0.438 M solution of potassium chromate (K2 CrO4) at 298 K is 1.063 g / mL . Cal

step 1 We want to recall the Roth's law. It says that it's a chemical law which is related to the vapor

The density of a 0.438 M solution of potassium chromate (K2...

The density of a 0.438 $\mathrm{M}$ solution of potassium chromate $\left(\mathrm{K}_{2} \mathrm{CrO}_{4}\right)$ at 298 $\mathrm{K}$ is 1.063 $\mathrm{g} / \mathrm{mL}$ . Calculate the vapor pressure of water above the solution. The vapor pressure of pure water at this temperature is 0.0313 atm. (Assume complete dissociation of the solute.)

Key Concepts

Solution Concentration Calculations

Determining the concentration of a solution involves relating the amount of solute to the total volume or mass of the solution. Accurate concentration calculations are necessary for computing mole fractions and for applying formulas related to colligative properties, especially when adjustments are required due to the presence of non-volatile solutes.

Raoult's Law

Raoult's Law states that the vapor pressure of the solvent in a solution is directly proportional to its mole fraction. When a non-volatile solute is added to a solvent, the mole fraction of the solvent decreases, leading to a lowering of the vapor pressure in comparison to that of the pure solvent.

Colligative Properties

Colligative properties are characteristics of solutions that depend solely on the number of solute particles present, not on their specific chemical identities. These properties include vapor pressure lowering, boiling point elevation, freezing point depression, and osmotic pressure, and they are crucial in understanding how solutes affect the physical properties of a solvent.

Ion Dissociation in Electrolytes

When an ionic compound dissolves in a solvent, it dissociates into multiple ions. This dissociation increases the total number of particles in the solution, which amplifies the colligative effects such as vapor pressure lowering. Accounting for complete dissociation is essential when applying Raoult's Law to electrolyte solutions.

Transcript

00:01 We want to recall the roth's law.

00:07 It says that it's a chemical law which is related to the vapor pressure of a solution, and that is dependent on mole fraction of a solute added to the solution.

00:17 So it's written in the formula of p equal to mole fraction times p.

00:24 Or p is the vapor pressure of the solution.

00:28 This is the mole fraction, and p .0 is the pure solvent vapor pressure.

00:36 So first we want to calculate the gram of solute and mass of solution.

00:44 So given the value as follow, the molarity of the solute is equal to 0 .438 molar, and the density of the solution is equal to 1 .063 grams per millimeter.

01:06 And the vapor pressure of water is equal to 0 .0313 atmosphere.

01:17 The molar mass for the solute, this is equal to 194 .2 grams per mole.

01:38 So now we can calculate the grams of the solute in potassium chromate equal to the molarity times the molarity.

01:51 Mass and that is equal to 194 .2 grams per mole times 0 .438 mole per liter and this is equal to 85 .0596 grams per liter.

02:24 So 85 .056 grams per liter.

02:26 So 85 .0596 grams of potassium chromate is present in a thousand milliliter or one liter of solution.

02:52 All right, so now we can calculate the mass of the solution.

02:59 The mass of the solution is equal to the density of the solution times the volume of the solution.

03:16 So that is 1 ,000 milliliter times 1 .063 grams per milliliter.

03:25 That's equal to 1063 grams.

03:32 So now that's the mass of the solution, and we can calculate the mass of the solvent by subtracting the mass of the solute from the mass of the solution minus mass of the solute.

03:58 So this is equal to 1063 grams minus 85 .0596 grams, this is equal to 97 .94 grams.

04:12 So this is the mass of the solvent.

04:19 So now we can calculate the most of water.

04:23 So the number of most equal to mass divided by molar mass.

04:28 So that's 977 .94 divided by the molar mass of water, which is 18 .016 grams...

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