1) How many moles of NH,CI and NH,OH must be added to 250 mL of water to make a
ID: 704019 • Letter: 1
Question
1) How many moles of NH,CI and NH,OH must be added to 250 mL of water to make a buffer of pH-9.0? Kb -1.8x10 2) How many milliters of 0.75 M HCI must be added to 120 mL of 0.90 M NaForm to make a buffer of pH -4.0? pKa 3.75 3) What volume of 0.40 M NaOH must be added to 100 mL of 0.60 M H,CO, to make a buffer of pH 10.0? H,CO, H+ + HCO,. KAI-4.2x10" 4) If the pH-3.75 at the endpoint of a titration, which indicator would you use? Circle one. Indicator Range Congo Red Methyl Orange 3.1-4.4 Bromocresol Green 3.8-5.4 3.0-5.0 Methyl Red 4.4-6.2Explanation / Answer
From the Henderson-Hasselbalch formula,
pOH = pKb + log[NH4+]/[NH4OH]
pOH = 14 - pH = 5
pKb =4.7
log[NH4+]/[NH4OH] = 5 - 4.74 = 0.26
[NH4+]/[NH4OH] = 1.82
So, 1 mole of NH4OH and 1.82 mole sof NH4OH added into 250 ml of water
only one question need to be answered.pls post remaining questions separately.
Related Questions
Navigate
Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.