Question

Show a sample calculation for the concentration of borax using 2.25 mL of 0.225 M HCl and 5.0 mL of borax solution. Make sure to include the units on all numbers and variables. You may find Equation 23.7 (B4O5(OH)4 (aq) + 2H(aq) --> 4B(OH)3(aq)) helpful in this set up. You must show all of your work for this question to receive full credit.

Answer 1

millimoles HCl = 2.25 x 0.225 = 0.506

complete balnced equation

Na₂B₄O₇ 10H₂O(borax) + 2 HCl ----------------> 2 NaCl + 4 H₃BO₃ + 5 H₂O

1                                           2

                                         0.506

millimoles of borax = 0.506 / 2 = 0.253

millimoles = molarity x volume

0.253 = molarity x 5.0

molarity = 0.0506 M

concentration of borax = 0.0506 M