Question

How many grams of dry NH4Cl need to be added to 2.10 L of a
0.700 *M* solution of ammonia, NH3, to prepare a buffer
solution that has a pH of 8.57? *K*b for ammonia is
1.8×10−5.

Answer #1

first convert the Kb in to pKa

Kb = 1.8×10^−5

pKb = -log(Kb) = -log(1.8×10^−5) = 4.74

pKa + pKb = 14

pKa = 14 - pKb = 14 - 4.74 = 9.26

now use the handerson equation

pH = pKa + log([A^{-}]/[HA])

here A^{-} = NH3

HA = NH4Cl

moles of NH3 = 0.7 M x 2.10 L = 1.47 moles

lets NH2Cl concentration = x

put all these values in the above eqation

8.57 = 9.26 + log(1.47/x)

log(1.47/x) = 8.57-9.26 = -0.69

1.47/x = 10^{-0.69}

1.47/x = 0.2042

x = 1.47 / 0.2042

x =7.2 moles

mass of NH4Cl = molar mass x moles

= 53.5 g /mol x 7.2 moles

= 385.2 grams

How many grams of dry NH4Cl need to be added to 2.50 L of a
0.700 M solution of ammonia, NH3, to prepare a buffer
solution that has a pH of 8.56? Kb for ammonia is
1.8×10−5.
Express your answer numerically in grams to three significant
figures.

How many grams of dry NH4Cl need to be added to 1.80 L of a
0.400 M solution of ammonia, NH3, to prepare a buffer solution that
has a pH of 8.83? Kb for ammonia is 1.8×10−5.

How many grams of dry NH4Cl need to be added to 2.20 L of a
0.500 M solution of ammonia, NH3, to prepare a buffer
solution that has a pH of 8.62? Kb for ammonia is
1.8×10−5.

How many grams of dry NH4Cl need to be added to 2.00 L of a
0.300 M solution of ammonia, NH3, to prepare a buffer solution that
has a pH of 8.64? Kb for ammonia is 1.8×10−5.

How many grams of dry NH4Cl need to be added to 1.60 L of a
0.800 M solution of ammonia, NH3, to prepare a buffer solution that
has a pH of 8.81? Kb for ammonia is 1.8×10−5.

How many grams of dry NH4Cl need to be added to 2.50 L of a
0.500 M solution of ammonia, NH3, to prepare a buffer solution that
has a pH of 8.69? Kb for ammonia is 1.8×10−5?

How many grams of dry NH4Cl need to be added to 2.50 L of a
0.800 Msolution of ammonia, NH3, to prepare a buffer
solution that has a pH of 8.84? Kb for ammonia is
1.8×10−5.

How many grams of dry NH4Cl need to be added to 1.80 L of a
0.400 M solution of ammonia, NH3, to prepare a buffer solution that
has a pH of 8.60? Kb for ammonia is 1.8×10−5. Express your answer
with the appropriate units.

How many grams of dry NH4Cl need to be added to 1.50 L of a
0.100 M solution of ammonia, NH3, to prepare a buffer solution that
has a pH of 8.82? Kb for ammonia is 1.8×10−5. Express your answer
with the appropriate units.

How many grams of dry NH4Cl need to be added to 1.60 L of a
0.100 M solution of ammonia, NH3 , to prepare a buffer
solution that has a pH of 8.55? Kb for ammonia is 1.8×10−5
. May you please show step by step how the answer was achieved?

ADVERTISEMENT

Get Answers For Free

Most questions answered within 1 hours.

ADVERTISEMENT

asked 20 minutes ago

asked 23 minutes ago

asked 26 minutes ago

asked 36 minutes ago

asked 56 minutes ago

asked 1 hour ago

asked 1 hour ago

asked 1 hour ago

asked 1 hour ago

asked 1 hour ago

asked 2 hours ago

asked 2 hours ago