Problem: The equilibrium constant for the reaction Hg2+(aq) + 2Cl−(aq) ⇌ HgCl2(aq) is 1.6 × 1013. Is HgCl2 a strong electrolyte or a weak electrolyte? What are the concentrations of Hg2+ and Cl– in a 0.015-M solution of HgCl2?

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FREE Expert Solution

• Strong electrolytes: dissociate completely in water; include soluble ionic salts, strong acids, and bases

a. Ionic salts: those that follow the rules of being soluble in solubility rules**

b. Strong acids: HCl, HBr, HI, HNO3, H2SO4, HClO4, HClO3

c. Strong bases: Group 1A and 2A (Ca and lower) metals paired with OH, H, O2–, or NH2


• Weak electrolytes: doesn’t dissociate completely in water; include weak acids and bases

a. Weak acids: include HF, HC2H3O2, HNO2, H2CO3, H3PO4

b. Weak bases: Be(OH)2, Mg(OH)2, NH3, NH4OH


• Nonelectrolytes: doesn’t dissociate at all; include molecular compounds

a. Alcohols: composed of carbon and hydrogen with a –OH group

b. Sugars: for example C6H12O6 (glucose) and C12H22O11 (sucrose)

c. Water (H2O)


**Solubility Rules:

Soluble Ionic Compounds:

Group 1A ions (Li+, Na+, K+, etc.) and Ammonium ion (NH4+) are soluble
 ▪ 
Nitrates (NO3-), Acetates (CH3COO- or C2H3O2-), and most Perchlorates (ClO4-) are soluble
 ▪ 
Cl-Br-, and I- are soluble except when paired with Ag+, Pb2+, Cu+, Hg22+
 ▪ 
Sulfates (SO42-) are soluble except those of Ca2+, Sr2+, Ba2+, Ag+, and Pb2+

• Insoluble Ionic Compounds:

▪ Hydroxides (OH-) and Sulfides (S2-) are insoluble except when with Group 1A ions (Li+, Na+, K+, etc.) and ammonium ion (NH4+) and Ca2+, Sr2+, Ba2+
 ▪ 
Carbonates (CO32-) and Phosphates (PO43-) are insoluble except when with Group 1A ions (Li+, Na+, K+, etc.) and ammonium ion (NH4+)

HgCl2 is, therefore, a strong electrolyte. It would dissociate completely in solution as:

HgCl2(aq) ⇋ Hg2+(aq) + 2 Cl-(aq)

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Problem Details

The equilibrium constant for the reaction Hg2+(aq) + 2Cl(aq) ⇌ HgCl2(aq) is 1.6 × 1013. Is HgCl2 a strong electrolyte or a weak electrolyte? What are the concentrations of Hg2+ and Cl in a 0.015-M solution of HgCl2?