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J. W. Hill, R. H. Petrucci, T. W. McCreary, & S. S. Perry General Chemistry 4th edition

Problem 15.80

Predict whether an aqueous solution can be made up to have the following concentrations or whether a chemical reaction must occur.

(a) 0.25 M CH3COONa and 0.15 M HI

(b) 0.050 M KNO2 and 0.18 M KNO3

(c) 0.0050 M Ca(OH)2 and 0.0010 M HNO3

(d) 0.20 M NH4Cl and 0.35 M NaOH






Answer:

(a) Write the solubilization reaction:

CH3COONa(aq)Na+(aq) + CH3COO(aq)

Acetate ion is basic, so will react with any acid present, so

HI(aq) + CH3COO(aq) CH3COOH(aq) + I(aq)

Thus, all of the HI will be consumed and the solution cannot contain 0.15 M HI.


(b) Write the solubilization reactions:

KNO2(aq)K+(aq) + NO2(aq)

KNO3(aq)K+(aq) + NO3(aq)

Nitrite ion is a base, but there is no acid present in solution so no further reactions occur and the given concentrations are compatible.


(c) Calcium hydroxide is a strong base and nitric acid is a strong acid, so reaction will occur

Ca(OH)2(aq) + 2 HNO3(aq) Ca2+(aq) + 2 NO3(aq) + 2 H2O(l)

The given concentrations are incompatible.


(d) Write the solubilization reaction:

NH4Cl(aq)NH4+(aq) + Cl(aq)

Ammonium ion is an acid and will react with any base present:

NH4+(aq) + NaOH(aq) Na+(aq) + NH3(aq) + H2O(l)

The given concentrations are incompatible.