Consider the titration of a 24.6 mL sample of 0.120 M RbOH with 0.105 M HCl. Det
ID: 1040991 • Letter: C
Question
Consider the titration of a 24.6 mL sample of 0.120 M RbOH with 0.105 M HCl. Determine each of the following.A) the initial pH B) the volume of added acid requires to reach the equivalence point C) the pH at 5.8 mL of added acid D) the pH at the equivalence point E) the pH after adding 5.9 mL of acid beyond the equivalence point Consider the titration of a 24.6 mL sample of 0.120 M RbOH with 0.105 M HCl. Determine each of the following.
A) the initial pH B) the volume of added acid requires to reach the equivalence point C) the pH at 5.8 mL of added acid D) the pH at the equivalence point E) the pH after adding 5.9 mL of acid beyond the equivalence point
A) the initial pH B) the volume of added acid requires to reach the equivalence point C) the pH at 5.8 mL of added acid D) the pH at the equivalence point E) the pH after adding 5.9 mL of acid beyond the equivalence point
Explanation / Answer
1)
The reaction happening will be
HCl + RbOH ----- RbCl + H2O
pOH = -log(OH-) = -log(0.120) = 0.9208
pH = 14 - pOH = 14 - 0.9208 = 13.0792
2)
At equivalence point
number of moles of acid = number of moles of base
V/1000 * 0.105 = 24.6/1000 * 0.120
V = 28.114 mL
3)
Number of moles of acid = 5.8/1000 * 0.105 = 0.000609 moles
Number of moles of base = 24.6/1000 * 0.120 = 0.002952 moles
Number of moles of base left = 0.002952 - 0.000609 = 0.002343 moles
Volume of solution = 24.6 + 5.8 = 30.4 mL
Molarity of OH- = 0.002343/30.4 * 1000 = 0.07707
pOH = -log(0.07707) = 1.113
pH = 14 - pOH = 14 - 1.113 = 12.887
4)
pH at equivalence point will be 7, since the titration of strong acid and strong base
5)
Number of moles of acid = 34.014/1000 * 0.105 = 0.00357147 moles
Number of moles of base = 24.6/1000 * 0.120 = 0.002952 moles
Number of moles of acid left = 0.00357147 - 0.002952 = 0.00061947 moles
Volume of solution = 24.6 + 34.014 = 58.614 mL
Molarity of H+ = 0.00061947/58.614 * 1000 = 0.01056863547
pH = -log(0.01056863547) = 1.975