Problem: Calculate the pH of the resulting solution if 20.0 mL of 0.200 M HCl(aq) is added to:a. 30.0 mL of 0.200 M NaOH(aq)b. 10.0 mL of 0.300 M NaOH(aq)

🤓 Based on our data, we think this question is relevant for Professor Delgado's class at FIU.

FREE Expert Solution

A. First, calculate the amount of acid and base that will react

molarity (volume) → moles

Recall:

molarity (M)=moles of soluteL of solution


*convert mL to L → 1 mL = 10-3 L


• 20.0 mL of 0.200 M HCl

moles HCl=20 mL×10-3 L1 mL×0.200 mol HClL


moles HCl = 4×10-3 mol HCl


• 30.0 mL of 0.200 M NaOH

moles NaOH=30mL×10-3 L1 mL×0.200 mol NaOHL


moles NaOH = 6×10-3 mol NaOH



Next, write the reaction equation between HCl and NaOH:

HCl is a strong acid and based on the Bronsted-Lowry definition, an acid is a proton (H+) donor.
NaOH is a strong base and based on Bronsted-Lowry definition, a base is a proton (H+) acceptor.
• HCl will donate a proton to NaOH

• The amount in moles of NaOH is greater than HCl. This means that HCl will be used up in the reaction while there will be some NaOH left unreacted


Reaction:

  HCl(aq)     +     NaOH(aq)            NaCl      +        H2O(l)
(acid)               (base)               (salt)     (water)



Determine how much NaOH will be left after the acid-base reaction


NaOH           6×10-3 mol

                     -

HCl               4×10-3 mol

                     2×10-3 mol NaOH



Determine the concentration of NaOH in the solution


Vsolution = VNaOH + VHCl


Vsolution = 30.0 mL +20.0 mL = 50.0 mL


M = 2×10-3mol NaOH50.0 mL(10-3 L1 mL)


M = 0.04 M NaOH


View Complete Written Solution
Problem Details

Calculate the pH of the resulting solution if 20.0 mL of 0.200 M HCl(aq) is added to:

a. 30.0 mL of 0.200 M NaOH(aq)
b. 10.0 mL of 0.300 M NaOH(aq)

Frequently Asked Questions

What scientific concept do you need to know in order to solve this problem?

Our tutors have indicated that to solve this problem you will need to apply the Strong Acid Strong Base Titrations concept. You can view video lessons to learn Strong Acid Strong Base Titrations. Or if you need more Strong Acid Strong Base Titrations practice, you can also practice Strong Acid Strong Base Titrations practice problems.

What professor is this problem relevant for?

Based on our data, we think this problem is relevant for Professor Delgado's class at FIU.