|
A 130.0 −mL buffer solution is 0.105 M in NH3 and 0.135 M in NH4BrNH4Br. The Kb value for NH3 is 1.76×10−5 |
Part A What mass of HCl can this buffer neutralize before the pH falls below 9.00? Part B If the same volume of the buffer were 0.265 M in NH3 and 0.390 M in NH4Br, what mass of HCl could be handled before the pH falls below 9.00? Express the mass in grams to three significant figures. |
Part A : mass of HCl = 0.0855 g
Part B : mass of HCl = 0.131 g
Explanation
Part A
concentration of NH3 = 0.105 M
volume of buffer = 130 mL = 0.130 L
initial moles of NH3 = (concentration of NH3) * (volume of buffer in Liter)
initial moles of NH3 = (0.105 M) * (0.130 L)
initial moles of NH3 = 0.01365 mol
Similarly, initial moles of NH4+ = 0.01755 mol
Let moles of HCl added = x
HCl is a strong acid which will neutralize NH3 to NH4+
final moles of NH3 = (initial moles of NH3) - (moles of HCl added)
final moles of NH3 = 0.01365 mol - x
final moles of NH4+ = (initial moles of NH4+) + (moles of HCl added)
final moles of NH4+ = 0.01755 mol + x
pH = 9.00
pOH = 14 - pH
pOH = 14 - 9.00
pOH = 5.00
Kb = 1.76 x 10-5
pKb = -log(Kb)
pKb = -log(1.76 x 10-5)
pKb = 4.75
According to Henderson - Hasselbalch equation,
pOH = pKb + log([conjugate acid] / [weak base])
pOH = pKb + log(final moles of NH4+ / final moles of NH3)
5.00 = 4.75 + log[(0.01755 mol + x) / (0.01365 mol - x)]
log[(0.01755 mol + x) / (0.01365 mol - x)] = 5.00 - 4.74
log[(0.01755 mol + x) / (0.01365 mol - x)] = 0.26
(0.01755 mol + x) / (0.01365 mol - x) = 100.26
(0.01755 mol + x) / (0.01365 mol - x) = 1.76
solving for x, x = 0.00235 mol
moles of HCl added = x = 0.00235 mol
mass of HCl added = (moles of HCl added) * (molar mass HCl)
mass of HCl added = (0.00235 mol) * (36.46 g/mol)
mass of HCl added = 0.0855 g
A 130.0 −mL buffer solution is 0.105 M in NH3 and 0.135 M in NH4BrNH4Br. The...
A 130.0 −mL buffer solution is 0.100 M in NH3 and 0.135 M in NH4Br. What mass of HCl can this buffer neutralize before the pH falls below 9.00? Express the mass in grams to three significant figures. If the same volume of the buffer were 0.265 M in NH3 and 0.400 M in NH4Br, what mass of HCl could be handled before the pH falls below 9.00? Express the mass in grams to three significant figures.
A 130.0 −mL buffer solution is 0.100 M in NH3 and 0.135 M in NH4Br. Part A What mass of HCl can this buffer neutralize before the pH falls below 9.00? Express the mass in grams to three significant figures. Part B If the same volume of the buffer were 0.270 M in NH3 and 0.390 M in NH4Br, what mass of HCl could be handled before the pH falls below 9.00?
A 130.0 −mL buffer solution is 0.110 M in NH3 and 0.135 M in NH4Br. The Kb value for NH3 is 1.76×10−5. If the same volume of the buffer were 0.270 M in NH3 and 0.390 M in NH4Br, what mass of HCl could be handled before the pH falls below 9.00?
A 120.0 ml. buffer solution 0.110 M NH3 and 0.135 M NH4Br. (Kb of NH3 is 1.76 x10^-5) Part B If the same volume of the butter were 0.265 M NH3 and 0.390 Min NH Br. What mass of HCl could be handled before the pH als below 9.00? Express the mass in grams to three significant
A 130.0 mL buffer solution is 0.105 molL?1 in NH3 and 0.135 molL?1 in NH4Br. 1.What mass of HCl will this buffer neutralize before the pH falls below 9.00? m=____g 2.If the same volume of the buffer were 0.270 molL?1 in NH3 and 0.400 molL?1 in NH4Br, what mass of HCl could be handled before the pH fell below 9.00? m=______g
A 110.0 −mL buffer solution is 0.110 M in NH3 and 0.135 M in NH4Br. Part A: What mass of HCl can this buffer neutralize before the pH falls below 9.00? Correct Answer: 8.51x10-2 g Part B: If the same volume of the buffer were 0.255 M in NH3 and 0.395 M in NH4Br, what mass of HCl could be handled before the pH falls below 9.00? Express the mass in grams to three significant figures. Please help with Part B!...
A 120.0 mL buffer solution is 0.100 M in NH3 and 0.130 M in NH4Br. (Kb of NH3 is 1.76×10−5.) What mass of HCl can this buffer neutralize before the pH falls below 9.00? If the same volume of the buffer were 0.250 M in NH3 and 0.400 M in NH4Br, what mass of HCl could be handled before the pH falls below 9.00?
A 120.0 −mL buffer solution is 0.110 M in NH3 and 0.125 M in NH4Br. You may want to reference (Pages 740 - 751) Section 17.2 while completing this problem. Part A What mass of HCl can this buffer neutralize before the pH falls below 9.00? Express the mass in grams to three significant figures. If the same volume of the buffer were 0.270 M in NH3 and 0.395 M in NH4Br, what mass of HCl could be handled before...
A 100.0 −mL buffer solution is 0.100 M in NH3 and 0.130 M in NH4Br. Part A: What mass of HCl can this buffer neutralize before the pH falls below 9.00? Part B: If the same volume of the buffer were 0.265 M in NH3 and 0.395 M in NH4Br, what mass of HCl could be handled before the pH falls below 9.00?
A 100.0 −mL buffer solution is 0.110 M in NH3 and 0.125 M in NH4Br. Part 1) What mass of HCl can this buffer neutralize before the pH falls below 9.00? Part 2) If the same volume of the buffer were 0.270 M in NH3 and 0.390 M in NH4Br, what mass of HCl could be handled before the pH falls below 9.00? For Part 1, I got 0.095 g as my answer, but it's incorrect.