buffers Q
Ka for methanoic acid is 1.78 × 10−4 mol dm−3 at 25°C.
buffer is prepared containing 2.35 × 10−2 mol of methanoic acid and 1.84 × 10−2 mol of sodium methanoate in 1.00 dm3 of solution.
(i) Calculate the pH of this buffer solution at 25°C.
I did this correct and worked it out as 3.64
however the next part I don't understand how to approach...
A 5.00 cm3 sample of 0.100 mol dm−3 hydrochloric acid is added to the buffer solution in part (c)(i).
Calculate the pH of the buffer solution after this addition.
I did the moles of H+ added as 5x10-4 but that's all I've got so far
buffer is prepared containing 2.35 × 10−2 mol of methanoic acid and 1.84 × 10−2 mol of sodium methanoate in 1.00 dm3 of solution.
(i) Calculate the pH of this buffer solution at 25°C.
I did this correct and worked it out as 3.64
however the next part I don't understand how to approach...
A 5.00 cm3 sample of 0.100 mol dm−3 hydrochloric acid is added to the buffer solution in part (c)(i).
Calculate the pH of the buffer solution after this addition.
I did the moles of H+ added as 5x10-4 but that's all I've got so far
Original post by medapplicant2020
Ka for methanoic acid is 1.78 × 10−4 mol dm−3 at 25°C.
buffer is prepared containing 2.35 × 10−2 mol of methanoic acid and 1.84 × 10−2 mol of sodium methanoate in 1.00 dm3 of solution.
(i) Calculate the pH of this buffer solution at 25°C.
I did this correct and worked it out as 3.64
however the next part I don't understand how to approach...
A 5.00 cm3 sample of 0.100 mol dm−3 hydrochloric acid is added to the buffer solution in part (c)(i).
Calculate the pH of the buffer solution after this addition.
I did the moles of H+ added as 5x10-4 but that's all I've got so far
buffer is prepared containing 2.35 × 10−2 mol of methanoic acid and 1.84 × 10−2 mol of sodium methanoate in 1.00 dm3 of solution.
(i) Calculate the pH of this buffer solution at 25°C.
I did this correct and worked it out as 3.64
however the next part I don't understand how to approach...
A 5.00 cm3 sample of 0.100 mol dm−3 hydrochloric acid is added to the buffer solution in part (c)(i).
Calculate the pH of the buffer solution after this addition.
I did the moles of H+ added as 5x10-4 but that's all I've got so far
The moles of acid added will interact with the conjugate base ions making more weak acid and removing moles of conjugate base.
Addition of strong acid to the buffer causes the following to happen: H+ + A- HA
Where H- is strong acid, in this case hydrochloric acid; A- is salt, in this case sodium methanoate; and HA is weak acid, in this case methanoic acid
Calculate the moles of hydrochloric acid added to the system, and hence determine how much sodium methanoate reacted and consequently how much methanoic acid was produced (the stoichiometry is 1:1, so the amount of sodium methanoate that reacted = the amount of methanoic acid that was produced)
This will leave you with new concentrations of both species, and since the buffer is of a volume of 1 dm3, the moles of each species is simply equal to their concentrations
You can therefore use the Henderson-Hasselbalch equation to determine how the pH changed due to this addition:
Where H- is strong acid, in this case hydrochloric acid; A- is salt, in this case sodium methanoate; and HA is weak acid, in this case methanoic acid
Calculate the moles of hydrochloric acid added to the system, and hence determine how much sodium methanoate reacted and consequently how much methanoic acid was produced (the stoichiometry is 1:1, so the amount of sodium methanoate that reacted = the amount of methanoic acid that was produced)
This will leave you with new concentrations of both species, and since the buffer is of a volume of 1 dm3, the moles of each species is simply equal to their concentrations
You can therefore use the Henderson-Hasselbalch equation to determine how the pH changed due to this addition:
(edited 4 years ago)
Quick Reply
Related discussions
- Chem help
- Problem with buffers in A2 Chemistry
- Biology enzymes question
- Grade Growth Chronicles | From C's to A's (23-24)
- ocr chemistry acid question
- Question about negative control pcr test!!!
- Chem a level buffers question
- Buffer solution help!!
- chemistry help for a level ocr
- Weak acid+alkali
- OCR A Level Chemistry Paper 1 H432/01 - 13th Jun 2022 [Exam Chat]
- A level chemistry help URGENT ‼️
- Buffer lost
- Buffer calculation help
- Can someone please help me with this question about buffers?
- AQA A Level Chemistry Acids and bases
- Chemistry a level buffers questions
- Buffer calculation question A level chemistry help
- Daily expenses.
- chemistry pH question HELP
Latest
Trending
Last reply 6 days ago
Im confused about this chemistry question, why does it form these productsTrending
Last reply 6 days ago
Im confused about this chemistry question, why does it form these products
