Question 1
Assume that an aqueous solution of hydroxide ion, OH
-, represented by unshaded spheres, is allowed to mix with a solution of an acid, H
nA, represented by gray spheres. Three possible outcomes are represented by boxes (a)-(c), where the black spheres represent A
n-, the anion of the acid. For clarity H
2O molecules are not shown.
Which outcome corresponds to the reaction:
H
3AsO
4 + 3 OH
- → 3 H
2O + AsO
43-?
◦ box (a)
◦ box (b)
◦ box (c)
◦ None of these
Question 2
The concentration of an aqueous solution of NaOCl can be determined by a redox titration with iodide ion in acidic solution:
OCl- (aq) + 2 I- (aq) + 2 H⁺ (aq) → Cl⁻ (aq) + I2 (aq) + H2O (l)
Assume that the black spheres in the buret represent I⁻ ions, the gray spheres in the flask represent OCl⁻ ions, the concentration of the I⁻ ions in the buret is 0.120 M, and the volumes in the buret and the flask are identical. What is the concentration of the NaOCl in the flask, and what fraction of the I⁻ solution in the buret must be added to the flask to react with all the OCl⁻ ions?
◦ 0.0600 M NaOCl; 2/3 of the I⁻ must be added.
◦ 0.0600 M NaOCl; 1/3 of the I⁻ must be added.
◦ 0.0400 M NaOCl; 2/3 of the I⁻ must be added.
◦ 0.0400 M NaOCl; 1/3 of the I⁻ must be added.
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