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A student who is performing this experiment pours a 6.50 1nL sample of the saturated borax solution into a 10111]. graduated cylinder after the...

Reaction (7): B4O5(OH)42-(aq) + 2H3O+(aq) + H2(I) ---> 4H3BO3 (aq)

Reaction (5): Na2B4O5(OH)4 * 8H2O(s) ---> 2Na+(aq) + B4O5(OH)42- (aq) + 8H2(I)

Screen Shot 2017-04-11 at 2.33.51 PM.png

Screen Shot 2017-04-11 at 2.33.51 PM.png

l. 2. 3. A student who is performing this experiment pours a 6.50 1nL sample of the saturated borax solution
into a 10—111]. graduated cylinder after the borax solution had cooled to a certain temperature T. The
student rinses the sample into a small flask using distilled water, and then titrates the solution with a
0.5003M HCl solution. To reach the endpoint of the titration, 10.15 mi. of the HCl solution is needed. Calculate the value of KSP for borax at temperature T. Be sure to show all your work; no credit will
be given otherwise.
Suggested procedure for doing this calculation: (:1). Calculate the number of moles of HCl that were added during the titration. (b). Use Reaction (7) in the Introduction to relate the number of moles of HCl to the number of motes of tetraboratc ion in the 6.50 mL sample. Calculate the number of moles of tetraborate ion in the
6.50 mL sample. (c). Calculate the concentration of tetraborate ions in the 6.50 mL sample. (d).Use Reaction (5) in the Introduction to relate the concentration of tetraborate ions to the
concentration of sodium ions. Calculate the concentration of sodium ion. (e). Use the concentrations of tetraborate ions and sodium ions to calculate the equilibrium constant
(Kw) at temperature Tusing equation (6). Fill in the blank: What is the pH at which the indicator bromocresol green is the following color?
(a) blue? (b) green? (c) yellow?
Explicitly cite your source (Let, a primary literature source) to obtain credit for this question. Do you expect AS" for the dissolution of borax to be a positive or negative number?
Explain your reasoning. (Hint: Look in your textbook!)

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(a) Moles of HCL = volume x... View the full answer

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(a) Moles of HCL = volume x concentration of HCl
10.15/1000x 0.5003 =0.005078 mol (b) HCl +H2O → H3O+ +ClMoles of H3O+ = Moles of HCl = 0.005078 mol
Moles of B4O5(OH)42 = 1/2 x moles of H3O+
½ x...

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