Question

In: Chemistry

A buffer solution consists of .195 M HCN and .22 M NaCN. a) what is the...

A buffer solution consists of .195 M HCN and .22 M NaCN.

a) what is the pH of this buffer solution?

b) you add 50 mL of .15 M HCl to 300.0 mL of this buffer solution. What will the pH be?

c) You add 20.0 mL of .26 M NaOH to 150.0 mL of this buffer solution. What will the pH be?

Expert Solution

a) pH = pKa + log [CN^-]/[HCN]

pKa of HCN = 9.31

pH = 9.31 + log [0.22] / [0.195]

pH = 9.36

b) initially

millimoles of NaCN = 300 x 0.22 = 66.0

millimoles of HCN = 300 x 0.195 = 58.5

millimoles of HCl added = 50 x 0.15 = 7.50

after HCl added

millimoles of HCN = 58.5 + 7.50 = 66.0

millimoles of NaCN = 66.0 - 7.50 = 58.50

[NaCN] = 58.50 / 350 = 0.167 M

[HCN] = 66.0 / 350 = 0.188 M

pH = 9.31 + log [0.167] / [0.188]

pH = 9.26

c) millimoles of HCN = 150 x 0.195 = 29.25

millimoles of NaCN = 150 x 0.22 = 33.0

millimoles of NaOH = 20.0 x 0.26 = 5.20

after NaOH added

millimoles of HCN = 29.25 - 5.20 = 24.05

millimoles of NaCN = 33.0 + 5.20 = 38.20

[HCN] = 24.05 / 170 = 0.141 M

[NaCN] = 38.20 / 170 = 0.224 M

pH = 9.31 + log [0.224] / [0.141]

pH = 9.51

queen_honey_blossom answered 2 years ago

A buffer solution is 0.390 M in HCN and 0.327 M in NaCN. If Ka for...

A buffer solution is 0.390 M in HCN and 0.327 M in NaCN. If Ka for HCN is 4.0×10-10, what is the pH of this buffer solution?

A buffer solution is 0.417 M in HCN and 0.326 M in NaCN . If Ka...

A buffer solution is 0.417 M in HCN and 0.326 M in NaCN . If Ka for HCN is 4.0×10-10, what is the pH of this buffer solution? A buffer solution is 0.418 M in H2SO3 and 0.253 M in NaHSO3. If Ka1 for H2SO3 is , what is the pH of this buffer solution? pH =

A buffer solution that is 0.325 M in HCN and 0.325 M in KCN has a...

A buffer solution that is 0.325 M in HCN and 0.325 M in KCN has a pH of 9.40. Addition of which of the following would increase the capacity of the buffer for added H3O+? both HCN and KCN pure water HCN KCN None of the Above One or more of these choices is the answer, please answer in that format. I have already asked this question and got the wrong answer. A buffer solution is made that is 0.388...

a. What is the pH of a buffer obtained by adding 9.8grams of NaCN (MW=49 g/mole) to 100ml of .20 M HCN?

Consider HCN (Ka= 5.8 x 10^-10) and NaCNa. What is the pH of a buffer obtained by adding 9.8grams of NaCN (MW=49 g/mole) to 100ml of .20 M HCN?b. What is the pH of this buffer after .01 moles of OH- are added to this solution?

Part A. Calculate the pH of a buffer solution that is 0.250 M in HCN and...

Part A. Calculate the pH of a buffer solution that is 0.250 M in HCN and 0.168 M in KCN. For HCN, Ka = 4.9×10−10 (pKa = 9.31). Part B. Calculate the pH of a buffer solution that is 0.240 M in HC2H3O2 and 0.190 M in NaC2H3O2. (Ka for HC2H3O2 is 1.8×10−5.) Part C. Consider a buffer solution that is 0.50 M in NH3 and 0.20 M in NH4Cl. For ammonia, pKb=4.75. Calculate the pH of 1.0 L of...

For a solution equimolar in HCN and NaCN, which statement is false? A. This is an...

For a solution equimolar in HCN and NaCN, which statement is false? A. This is an example of the common-ion effect. B. Addition of NaOH will increase [CN�] and decrease [HCN]. C. Addition of more NaCN will shift the acid-dissociation equilibrium of HCN to the left. D. [H+] is equal to Ka. E. [H+] is larger than it would be if only the HCN were in solution.

1.Calculate the pH of a buffer solution that is 0.249 M in HCN and 0.175 M...

1.Calculate the pH of a buffer solution that is 0.249 M in HCN and 0.175 M in KCN. For HCN, Ka = 4.9×10−10 (pKa = 9.31). 2.Calculate the pH of a buffer solution that is 0.210 M in HC2H3O2 and 0.200 M in NaC2H3O2. (Ka for HC2H3O2 is 1.8×10−5.) 3.Consider a buffer solution that is 0.50 M in NH3and 0.20 M in NH4Cl. For ammonia, pKb=4.75. Calculate the pH of 1.0 L of the original buffer, upon addition of 0.020...

You are asked to prepare 1.6 L of a HCN/NaCN buffer that has a pH of...

You are asked to prepare 1.6 L of a HCN/NaCN buffer that has a pH of 9.90 and an osmotic pressure of 1.12 atm at 298 K. What masses of HCN and NaCN should you use to prepare the buffer? (Assume complete dissociation of NaCN.) Express your answers using two significant figures separated by a comma.

You are asked to prepare 4.0 L of a HCN/NaCN buffer that has a pH of...

You are asked to prepare 4.0 L of a HCN/NaCN buffer that has a pH of 9.48 and an osmotic pressure of 1.44 atm at 298 K. Part A What masses of HCN and NaCN should you use to prepare the buffer? (Assume complete dissociation of NaCN.)

You are asked to prepare 1.4 L of a HCN/NaCN buffer that has a pH of...

You are asked to prepare 1.4 L of a HCN/NaCN buffer that has a pH of 9.78 and an osmotic pressure of 1.11 atm at 298 K. What masses of HCN and NaCN should you use to prepare the buffer? (Assume complete dissociation of NaCN.)