The solubility of calcium sulfate at 30^∘ C is 0.209 g / 100 . mL solution. Calculate its Ksp

Name: Problem 73, Chapter 19: Chemistry: The Molecular Nature of Matter and Change
Uploaded: 2020-06-14T04:23:21-08:00
Duration: 4 min 44 s
Channel: Nicole Powell
Description: The solubility of calcium sulfate at 30^∘ C is 0.209 g / 100 . mL solution. Calculate its Ksp

The solubility of calcium sulfate at 30^∘ C is 0.209 g / 100...

Key Concepts

Stoichiometry

Stoichiometry involves using the balanced chemical equation of the dissolution process to relate the amount of solute that dissolves to the concentrations of the ions produced. It ensures that the equilibrium expression, such as that for Ksp, accurately reflects the behavior of the system.

Solubility Product Constant (Ksp)

The solubility product constant, Ksp, is an equilibrium constant specific to the dissolution of a sparingly soluble ionic compound. It is defined as the product of the concentrations of the resulting ions, each raised to the power of its stoichiometric coefficient in the balanced equation, and is used to predict precipitation and solubility behavior.

Solubility

Solubility refers to the maximum amount of a substance that can dissolve in a given amount of solvent at a specific temperature, generally expressed in grams per volume. It is essential for understanding how much of a compound will go into solution and sets the stage for further equilibrium calculations.

Molar Solubility

Molar solubility is a conversion of solubility from grams per volume into moles per liter. This conversion requires the use of the compound’s molar mass and is critical when calculating concentrations of ions in the equilibrium expression.

Transcript

00:01 The equation for a saturated solution of calcium sulfate is c .a .s .o .4 solid partially dissociates to c .a.

00:13 2 plus aqueous plus s .o .42 minus aqueous.

00:22 That means our ksp is equal to the concentration of ca2 plus times the concentration of s .o4 2 minus.

00:33 In order to calculate the value of the ksp, we have to start by converting our salubility here into molar salubility.

00:44 What that means is we have to go from grams over milliliters to moles over liters, which is just molarity.

00:59 So we have 0 .209 grams of c .a .s .4 in 100 milliliters of solution.

01:09 Let's start by doing the easy part of converting milliliters to liters.

01:14 There are 1 ,000 milliliters in 1 liter, and just to make sure we're canceling our units correctly, there are milliliters on top and milliliters on bottom, and we're left with liters on the bottom, which is what we're looking for.

01:30 Now we just have to convert our grams to moles, and in order to do that, we need to know the molar mass of caso4.

01:38 So we can check our periodic table to look up our molar mass of calcium, sulfur, and we just have to convert our grams to moles.

01:54 In order to do that, we need to know the molar mass of caso4.

01:59 So we can check our periodic table to find the molar mass of calcium, sulfur, and oxygen, and add all those together where we're adding one times the molar mass of calcium, one times the molar mass of sulfur, and four times the molar mass of oxygen, and then we'll get the total molar mass of caso4.

02:25 Once we do that, we get a value of 136 .14 grams per mole, which means for every mole of calcium sulfate, we have 136 .14 grams per mole, which means for every mole of calcium sulfate, 36 .14 grams of calcium sulfate.

02:45 Now we can make sure our units cancel...

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