Chapter 10: Problem 96
Lithium salts, such as lithium carbonate, are used to treat manic-depressives. What is the solubility product for lithium carbonate if 1.36 grams of \(\mathrm{Li}_{2} \mathrm{CO}_{3}\) dissolve in \(100 \mathrm{~mL}\) of water?
Short Answer
Expert verified
Ksp for \( \text{Li}_2\text{CO}_3 \) is approximately 0.0249.
Step by step solution
01
Calculate Molar Mass
First, calculate the molar mass of lithium carbonate \( \text{Li}_2\text{CO}_3 \). The molar masses are: Li = 6.94 g/mol, C = 12.01 g/mol, O = 16.00 g/mol. Therefore, \( \text{Li}_2\text{CO}_3 \) has a molar mass of \( 2(6.94) + 12.01 + 3(16.00) = 73.89 \text{ g/mol} \).
02
Calculate Moles of Li2CO3 Dissolved
Convert the dissolved \( \text{Li}_2\text{CO}_3 \) into moles. Given 1.36 g of \( \text{Li}_2\text{CO}_3 \): \( \frac{1.36 \, \text{g}}{73.89 \, \text{g/mol}} = 0.0184 \, \text{mol} \).
03
Calculate Concentration of Li2CO3
Calculate the molarity of the lithium carbonate solution. Since it dissolves in 100 mL (or 0.1 L) of water, the concentration is \( \frac{0.0184 \, \text{mol}}{0.1 \, \text{L}} = 0.184 \, \text{M} \).
04
Write Dissociation Equation
The dissociation equation for lithium carbonate is \( \text{Li}_2\text{CO}_3(s) \rightleftharpoons 2\text{Li}^+(aq) + \text{CO}_3^{2-}(aq) \). Each formula unit produces 2 lithium ions and 1 carbonate ion.
05
Set up Ksp Expression
Calculate the solubility product (Ksp). The formula is \( K_{sp} = [\text{Li}^+]^2 \times [\text{CO}_3^{2-}] \). From the dissociation, \([\text{Li}^+] = 2 \times 0.184 = 0.368 \, \text{M}\) and \([\text{CO}_3^{2-}] = 0.184 \, \text{M}\).
06
Calculate Ksp
Substitute the concentrations into the Ksp expression: \( K_{sp} = (0.368)^2 \times (0.184) = 0.024876 \). Thus, the solubility product is approximately 0.0249.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Lithium Carbonate
Lithium carbonate, denoted as \( \text{Li}_2\text{CO}_3 \), is a vital compound in the pharmaceutical industry, particularly in the treatment of bipolar disorder.This compound appears as a white, powdery substance and stands out due to its limited solubility in water.When dissolved, it dissociates into lithium ions (\( \text{Li}^+ \) and carbonate ions (\( \text{CO}_3^{2-} \).
- Applications: It is predominantly used in the medical field to stabilize mood swings in manic-depressive patients.
- Solubility: Despite its therapeutic benefits, lithium carbonate is sparingly soluble, making its precise solubility critical for medical dosages.
Chemical Equilibrium
Chemical equilibrium occurs when a chemical reaction's forward and reverse processes happen at the same rate, resulting in a stable state.In the context of lithium carbonate, this dynamic is crucial as it informs how the compound dissolves and maintains balance in solution.When \( \text{Li}_2\text{CO}_3 \) is dissolved in water, it achieves equilibrium between its solid form and the ions in the solution.
- Dissociation Equation: The dissociation of lithium carbonate is represented as \( \text{Li}_2\text{CO}_3(s) \rightleftharpoons 2\text{Li}^+(aq) + \text{CO}_3^{2-}(aq) \). Each mole of \( \text{Li}_2\text{CO}_3 \) produces 2 moles of \( \text{Li}^+ \) and 1 mole of \( \text{CO}_3^{2-} \).
- Equilibrium Considerations: The degree of dissolution and the concentrations of ions are dictated by the solubility product, \( K_{sp} \).
Molar Mass Calculation
Understanding molar mass calculation is fundamental in determining the amount of a substance in a chemical reaction.In this exercise, calculating the molar mass of lithium carbonate (\( \text{Li}_2\text{CO}_3 \)) is a critical step.Each element in the compound contributes to its total mass based on its atomic weight.- Lithium (Li) has an atomic mass of 6.94 g/mol.- Carbon (C) has an atomic mass of 12.01 g/mol.- Oxygen (O) comes in at 16.00 g/mol.The formula for lithium carbonate consists of two lithium atoms, one carbon atom, and three oxygen atoms.Thus, the molar mass is:\[ 2(6.94) + 12.01 + 3(16.00) = 73.89 \text{ g/mol} \]Calculating this value is crucial when converting grams of a substance to moles, which is necessary for further calculations such as determining the concentration or the \( K_{sp} \). Knowing how to calculate molar mass allows students to confidently handle and predict outcomes in chemical reactions.