Ch.16 - Aqueous Equilibrium WorksheetSee all chapters
All Chapters
Ch.1 - Intro to General Chemistry
Ch.2 - Atoms & Elements
Ch.3 - Chemical Reactions
BONUS: Lab Techniques and Procedures
BONUS: Mathematical Operations and Functions
Ch.4 - Chemical Quantities & Aqueous Reactions
Ch.5 - Gases
Ch.6 - Thermochemistry
Ch.7 - Quantum Mechanics
Ch.8 - Periodic Properties of the Elements
Ch.9 - Bonding & Molecular Structure
Ch.10 - Molecular Shapes & Valence Bond Theory
Ch.11 - Liquids, Solids & Intermolecular Forces
Ch.12 - Solutions
Ch.13 - Chemical Kinetics
Ch.14 - Chemical Equilibrium
Ch.15 - Acid and Base Equilibrium
Ch.16 - Aqueous Equilibrium
Ch. 17 - Chemical Thermodynamics
Ch.18 - Electrochemistry
Ch.19 - Nuclear Chemistry
Ch.20 - Organic Chemistry
Ch.22 - Chemistry of the Nonmetals
Ch.23 - Transition Metals and Coordination Compounds

Solution: What is the minimum S2− concentration that will cause ZnS to start precipitating from a 0.10 M solution of Zn(NO3)2, a very soluble salt? Ksp for ZnS is 1.1 × 10−21.

Solution: What is the minimum S2− concentration that will cause ZnS to start precipitating from a 0.10 M solution of Zn(NO3)2, a very soluble salt? Ksp for ZnS is 1.1 × 10−21.

Problem

What is the minimum S2− concentration that will cause ZnS to start precipitating from a 0.10 M solution of Zn(NO3)2, a very soluble salt? Ksp for ZnS is 1.1 × 10−21.

Solution

For this problem, we’re being asked to calculate the concentration of S2– needed in order to precipitate ZnS from a 0.10 M Zn(NO3)2 solution.


Since the compounds are ionic compounds, they form ions when dissociating in water. The dissociation of ZnS and Zn(NO3)2 in water are as follows:


The sulfide ion, S2–, has a charge of –2. Zinc then has a charge of +2:

ZnS(s)  Zn2+(aq) + S2–(aq)


The nitrate ion, NO3, has a charge of –1. Zinc then has a charge of +2:

Zn(NO3)2  Zn2+(aq) + 2 NO3(aq)


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