Question

Consider the titration of a 26.9 −mL sample of 0.115 M RbOH with 0.100 M HCl. Determine each of the following.

A. the initial pH?

B. the volume of added acid required to reach the equivalence point

Answer 1

since RbOH is a strong base concentration of RbOH = [OH-]

pOH = -log[OH-]

pOH = -log[0.115]

pOH = 0.94

pH = 14-POH = 14-0.94

pH = 13.06

PartB

no of moles of HCl = molarity of HCl x volume in liters

= 0.115 x 0.0269 L

= 0.0031 moles

write the balanced equation

RbOH + HCl -----> RbCl + H2O

from this equation it is clear that one mole of RbOH required one mole of HCl

0.0031 moles required 0.0031 moles HCl

so no of moles of HCl = 0.0031

now we know the moles of HCl and molarity of HCl

volume of HCl = moles of HCl / molarity of HCl

= 0.0031/0.1

= 0.031L iters or

= 31 mL 0.1M HCl