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Solubility and Concentration of Ions

What is the pCl- value for a solution that is 0.040 M KCl and 0.020 M in MgCl2?

a) 0.6

b) 1.1

c) 1.2

d) 1.4

e) 1.7

II) The 90% confidence limits for ppm magnesium in a sample are 3.56±0.32 ppm Mg. This indicates that the interval of 3.24 ppm Mg to 3.88 ppm Mg

a) has a 90 % chance of enclosing the true value of ppm Mg in the sample.

b) has a 90 % chance of enclosing the experimental mean.

c) encloses 90 % of the measured data points.

d) spans one standard deviation above and below the mean.

III) Which of the compounds below is NOT a primary standard?

a) AgNO3

b) Na2CO3

c) NaOH

d) Potassium hydrogen phthalate (KHP)

IV) Which of the following compounds has the highest solubility in water? The Ksp value for each salt is given in parenthesis.

a) FeS (8.0 × 10-19)

b) HgI2 (1.0 × 10-19)

c) AgI (8.3 × 10-17)

d) AgBr (5.0 × 10-13)

V) HA and A- are a conjugate acid/base pair. Which of the solutions below has the greatest buffer capacity.

a) A mixture containing 0.500 mol of HA and 0.500 mol of A-.

b) A mixture containing 0.0500 mol of HA and 0.0500 mol of A-.

c) A mixture containing 0.300 mol of HA and 0.300 mol of A-.

d) A mixture containing 0.500 mol of HCl and 0.500 mol of NaOH.

e) A mixture containing 0.300 mol of HCl and 0.300 mol of A-.
GMU, CHEM 321 Final Initial _____________ Page 2 of 9
VI) Consider a system containing the diprotic acid H2CO3 and its conjugates. The Kb2 expression relates to which of the following reactions:

a) H2CO3 + H2O ↔ HCO3- + H3O+

b) HCO3- + H2O ↔ CO32- + H3O+

c) HCO3- + H2O ↔ H2CO3 + OH-

d) CO32- + H2O ↔ HCO3- + OH-

e) H2CO3 + 2H2O ↔ CO32- + 2H3O+

VII) What is the ionic strength of a 0.10 M solution of Mg(NO3)2?

a) 0.10 M

b) 0.20 M

c) 0.30 M

d) 0.40 M

e) 0.60 M

VIII) The mass expression for an aqueous solution saturated with MgF2 is

a) [Mg+2] = 2[F-]

b) [Mg+2] = 2[F-] + 2[HF]

c) 2[Mg+2] = [F-]

d) 2[Mg+2] = [F-] + [HF]

e) [Mg+2] = 2[F-] + 2[H3O+]


Solution Summary

This solution explains:

1) How to find the pCl- value for a solution involving two chloride compounds.

2) How to use confidence limits.

3) Which compound out of a set of compounds is a primary standard.

4) How to use Ksp to determine solubility.

5) How to determine buffer capacity of a solution.

6) How to write a Kb2 expression.

7) How to calculate ionic strength.

8) How to write a mass expression.