更新1:
Calculate the ratio of CH3NH2 to CH3NH3Cl required to create a buffer with pH = 10.18. thank you.
Calculate the ratio of CH3NH2 to CH3NH3Cl required to create a buffer with pH = 10.18.?
回答 (2)
2018-04-03 9:45 pm
Refer to: https://answers.yahoo.com/question/index?qid=20180403124222AAuzYQy
Kb for CH₃NH₂ = 4.2 × 10⁻⁴
(Different sources give slightly different values of Kb. This gives slightly different answer.)
Henderson-Hasselbalch equation :
pOH = pKb + log([CH₃NH₃⁺]/[CH₃NH₂])
pKw - pH = -log(Kb) - log([CH₃NH₂]/[CH₃NH₃⁺])
14.00 - 10.18 = -log(4.2 × 10⁻⁴) - log([CH₃NH₂]/[CH₃NH₃⁺])
log([CH₃NH₂]/[CH₃NH₃⁺]) = -log(4.2 × 10⁻⁴) - 3.82
[CH₃NH₂]/[CH₃NH₃⁺] = 10^{-log(4.2 × 10⁻⁴) - 3.82} = 0.36
[CH₃NH₂] : [CH₃NH₃⁺] = 0.36 : 1
Kb for CH₃NH₂ = 4.2 × 10⁻⁴
(Different sources give slightly different values of Kb. This gives slightly different answer.)
Henderson-Hasselbalch equation :
pOH = pKb + log([CH₃NH₃⁺]/[CH₃NH₂])
pKw - pH = -log(Kb) - log([CH₃NH₂]/[CH₃NH₃⁺])
14.00 - 10.18 = -log(4.2 × 10⁻⁴) - log([CH₃NH₂]/[CH₃NH₃⁺])
log([CH₃NH₂]/[CH₃NH₃⁺]) = -log(4.2 × 10⁻⁴) - 3.82
[CH₃NH₂]/[CH₃NH₃⁺] = 10^{-log(4.2 × 10⁻⁴) - 3.82} = 0.36
[CH₃NH₂] : [CH₃NH₃⁺] = 0.36 : 1
2018-04-03 9:07 pm
use the HH equation
pH = pKa + log([A-]/HA])
look up pKa of CH3NH3Cl ( or calculate it from pKb CH3NH2) and calculate ratio
pH = pKa + log([A-]/HA])
look up pKa of CH3NH3Cl ( or calculate it from pKb CH3NH2) and calculate ratio
收錄日期: 2021-05-01 22:24:45
原文連結 [永久失效]:
https://hk.answers.yahoo.com/question/index?qid=20180403124222AAuzYQy