# analytical chemistry

A solution containing 0.40 M B (a weak base) and 0.20 M BH+ (the salt of the weak
base) has a pH = 10.30. What is the pH after 25 mmol of HCl is added to 250 mL of this
solution?

1. 👍 0
2. 👎 0
3. 👁 49
1. First use the Henderson-Hasselbalch equation and solve for pKa.
pH = pKa + log (base)/(acid)
10.30 = pKa + log [0.4/0.2]
pKa = ?

mmols B initially = 0.4 x 250 = 100
mmols BH^+ initially = 0.2 x 250 = 50

..........B + H^+ ==> BH^+
I........100...0......50
C........-25...-25....+25
E.........75...0.......75

Using pKa from above, substitute the E line into a new HH equation and solve for pH.
Since B = BH^+ then the log term will be zero and the new pH will equal pKa.

1. 👍 0
2. 👎 0
2. 10

1. 👍 0
2. 👎 0
posted by minshee

## Similar Questions

1. ### Chemistry

If an equal number of moles of the weak acid HOCN and the strong base KOH are added to water, the resulting solution will be acidic, basic or neutral? There is a complicated answer and a sensible answer. Both arrive at the same

asked by Joel on April 27, 2007
2. ### Chemistry

Why is the equivalence point of a weak acid-strong base titration above 7.0? How can the data reflect this? The titration of a weak acid with a srong base produces a salt of the two. The anion is hydrolyzed in water solution but

asked by Anonymous on April 23, 2007
3. ### Chemistry

I have an assignment Q A 0.1 mol L-1 water solution of NH4CH3CO2 has a pH of approx 7. Explain this using two equations. I have one equation CH3COO-(aq) + H2O(l) --> CH3COOH(aq) + OH-(aq) What could the other equation be?

asked by Fiona on May 18, 2007
4. ### Chemistry

A buffer is prepared by mixing 110. mL of 0.442 M HCl and 0.545 L of 0.400 M sodium acetate. How many grams of KOH must be added to 0.500 L of the buffer to change the pH by 0.10 units? The pH I have calculated to be 5.28. What do

asked by Christina on April 2, 2007
5. ### chem

Can someone please help me by explaining and correcting me? 1) A 0.057M solution of a weak acid has a pH of 4.93. Determine the ionization constant, Ka, of the acid. a) 2.1 x 10^-4 b) 2.4 x 10^-9 c) 4.1 x 10^-8 d) 2.8 x 10^-7 e)

6. ### chemistry

Hello! Please correct me if I'm wrong. For the following compound, predict whether the solution is acidic, basic, or neutral and why: NH4Cl. a) acidic, NH4Cl is the salt of a weak base b) neutral because there is no hydrolysis c)

7. ### Chemistry

NH3 is a weak base (Kb = 1.8 × 10–5) and so the salt NH4Cl acts as a weak acid. What is the pH of a solution that is 0.049 M in NH4Cl at 25 °C?

asked by Todd Mike on October 16, 2015
8. ### Chemistry

NH3 is a weak base (Kb = 1.8 × 10–5) and so the salt NH4Cl acts as a weak acid. What is the pH of a solution that is 0.050 M in NH4Cl?

asked by Jefferson on March 9, 2013
9. ### CHEMISTRY

HOW CAN U TELL IF HNO3 +KNO3 IS A BUFFER SOLUTION A buffer solution must contain a weak acid and its conjugate base OR a weak base and its conjugate acid. HNO3 is a strong base and KNO3 is the salt of a strong base (KOH) and a

asked by CANDY on February 27, 2007
10. ### Chemistry

In the titration of a weak acid with a strong base, the pH at the equivalence point is affected mostly by a.hydrolysis (reaction with water) of the weak acid b.the dissociation of water molecules c.the presence of excess base

asked by Cheryl on May 26, 2011

More Similar Questions