Question

In: Chemistry

A 200.0 mL buffer solution is 0.360 M NH3 and 0.250 M NH4Br. What mass of...

A 200.0 mL buffer solution is 0.360 M NH3 and 0.250 M NH4Br. What mass of HCl does this buffer neutralize before pH falls below 8.80?

Solutions

Expert Solution

Volume of buffer = 200.0 ml

= 200 ml * 1.0 L/1000 ml

= 0.200 L

Number of moles = molarity * volume in L

Initial moles of NH3 = 0.360 x 0.200

= 0.072 mol

Initial moles of NH4+ = initial moles of NH4Br

= 0.250* 0.200

= 0.05 mol

We know that

pKb of NH3 = 1.8 x 10^-5

Kw= 1.0 x 10 ^-14

pKa of NH4+ = Kw/pKb of NH3

= 1.0 x 10 ^-14/1.8 x 10^-5

= 5.556 x 10^-10

And pK a = - log Ka

= - log 5.556 x 10^-10

= 9.25

NH3 + HCl => NH4+ + Cl-

Let us if x be the moles of HCl added

Moles of NH3 = 0.072 - x

Moles of NH4+ = 0.05 + x

Henderson-Hasselbalch equation:

pH = pKa + log([NH3]/[NH4+])

8.80 = 9.25 + log(moles of NH3/moles of NH4+)

8.80 = 9.25 + log ((0.072 – x )/( 0.05 + x))

- 0.45 = log ((0.072 – x )/( 0.05 + x))

((0.072 – x )/( 0.05 + x)) = 10^- 0.45

((0.072 – x )/( 0.05 + x))=0.355

0.072-x = 0.01775 + 0.355 x

0.05424= 1.355x

x = 0.0400 moles

Moles of HCl added = 0.400 mol

Mass of HCl added = moles x molar mass

= 0.0400 x 36.46 = 1.46 g

queen_honey_blossom answered 1 year ago

Next > < Previous

Related Solutions

A 130.0 −mL buffer solution is 0.105 M in NH3 and 0.135 M in NH4Br. What...

A 130.0 −mL buffer solution is 0.105 M in NH3 and 0.135 M in NH4Br. 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 0.390 M in NH4Br, what mass of HCl could be handled before the pH falls below 9.00? Need answer in grams. PS the answer is not .092

A 130.0 −mL buffer solution is 0.100 M in NH3 and 0.125 M in NH4Br. What...

A 130.0 −mL buffer solution is 0.100 M in NH3 and 0.125 M in NH4Br. What mass of HCl can this buffer neutralize before pH falls below 9.00? Please help and show work. I keep getting 2.5-2.85 g of HCl. I cannot figure this out, it keeps saying its the incorrect answer!

A 130.0 −mL buffer solution is 0.105 M in NH3 and 0.135 M in NH4Br. A)...

A 130.0 −mL buffer solution is 0.105 M in NH3 and 0.135 M in NH4Br. A) What mass of HCl can this buffer neutralize before the pH falls below 9.00? B) If the same volume of the buffer were 0.250 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 0.100 M in NH3 and 0.135 M in NH4Br. A)...

A 130.0 −mL buffer solution is 0.100 M in NH3 and 0.135 M in NH4Br. A) What mass of HCl can this buffer neutralize before the pH falls below 9.00? B) If the same volume of the buffer were 0.270 M in NH3 and 0.400 M in NH4Br, what mass of HCl could be handled before the pH falls below 9.00?

A 100.0 −mL buffer solution is 0.105 M in NH3 and 0.135 M in NH4Br. A....

A 100.0 −mL buffer solution is 0.105 M in NH3 and 0.135 M in NH4Br. A. What mass of HCl could this buffer neutralize before the pH fell below 9.00 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 fell below 9.00? I know for A i have tried .19g, .0915, and .5`3 using three different methods. I have no idea...

A 130.0 −mL buffer solution is 0.105 M in NH3 and 0.135 M in NH4Br. A)...

A 130.0 −mL buffer solution is 0.105 M in NH3 and 0.135 M in NH4Br. A) What mass of HCl could this buffer neutralize before the pH fell below 9.00? answer to this was 0.088g 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 fell below 9.00?

A 100.0 −mL buffer solution is 0.110 M in NH3 and 0.125 M in NH4Br. A....

A 100.0 −mL buffer solution is 0.110 M in NH3 and 0.125 M in NH4Br. A. If the same volume of the buffer were 0.260 M in NH3 and 0.395 M in NH4Br, what mass of HCl could be handled before the pH fell below 9.00? B. What mass of HCl could this buffer neutralize before the pH fell below 9.00?

A 130.0 −mL buffer solution is 0.100 M in NH3 and 0.130 M in NH4Br. Part...

A 130.0 −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 0.255 M in NH3 and 0.400 M in NH4Br, what mass of HCl could be handled before the pH falls below 9.00?

A 130.0 −mL buffer solution is 0.100 M in NH3 and 0.135 M in NH4Br. a.Part...

A 130.0 −mL buffer solution is 0.100 M in NH3 and 0.135 M in NH4Br. a.Part A What mass of HCl can this buffer neutralize before the pH falls below 9.00? b.Part B If the same volume of the buffer were 0.255 M in NH3 and 0.400 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. (Kb...

A 130.0 mL buffer solution is 0.110 M in NH3 and 0.135 M in NH4Br. (Kb of NH3 is 1.76×10−5.) a.)What mass of HCl can this buffer neutralize before the pH falls below 9.00? b.)If the same volume of the buffer were 0.255 M in NH3 and 0.400 M in NH4Br, what mass of HCl could be handled before the pH falls below 9.00?

Subjects