Question

In: Chemistry

Part A How many moles of HF (Ka=6.8×10−4) must be added to water to form 0.230...

Part A

How many moles of HF (Ka=6.8×10−4) must be added to water to form 0.230 L of solution with a pH of 2.50?

Express your answer using two significant figures.

n=____mol

Solutions

Expert Solution

Answer – We are given, pH = 2.50 , volume = 0.230 L , Ka = 6.8*10-4

We know,

[H3O+] = 10-pH

            = 10-2.50

             = 0.00316 M

We need to put ICE chart and assume [HF] = Y

    HF + H2O <-----> H3O+ + F-

I Y                              0        0

C -x                            +x      +x

E Y-x                     0.00316   +x

So at equilibrium, x = [H3O+] = 0.00316 M

So,

Ka = [H3O+][F-] / [HF]

6.8*10-4 = 0.00316 *0.00316 / (Y-0.00316)

6.8*10-4 (Y-0.00316) = 1.0*10-5

6.8*10-4 Y -2.15*10-6 = 1.0*10-5

6.8*10-4 Y = 1.0*10-5 + 2.15*10-6

                 = 1.21*10-5

So, Y = 0.0179 M

So, [HF] = 0.0179 M

We know

Moles of HF = 0.0179 M * 0.230 L

         = 0.00411 moles of HF

0.00411 moles of HF (Ka=6.8×10−4) must be added to water to form 0.230 L of solution with a pH of 2.50


Related Solutions

Part A How many moles of HF (Ka=6.8
Part A How many moles of HF (Ka=6.8
Part A If a solution of HF (Ka=6.8×10−4) has a pH of 2.80, calculate the concentration...
Part A If a solution of HF (Ka=6.8×10−4) has a pH of 2.80, calculate the concentration of hydrofluoric acid. Express your answer using two significant figures. n = mol
Part A If a solution of HF (Ka=6.8×10−4) has a pH of 2.80, calculate the concentration...
Part A If a solution of HF (Ka=6.8×10−4) has a pH of 2.80, calculate the concentration of hydrofluoric acid. Express your answer using two significant figures. n = mol
How many moles of KF should be added to 0.50 L of a 0.10 M HF...
How many moles of KF should be added to 0.50 L of a 0.10 M HF solution to prepare a buffer with a pH of 2.84?
How many moles of NH3 (Kb= 1.8 × 10‒5) must be dissolved in water in order...
How many moles of NH3 (Kb= 1.8 × 10‒5) must be dissolved in water in order to prepare 0.616 L of solution with a pH of 11.22?
What is the percent ionization for a 0.300M HF solution? Ka for HF is 6.3×10-4.
What is the percent ionization for a 0.300M HF solution? Ka for HF is 6.3×10-4.
How many moles of potassium chloride must be added to the solution to completely precipitate 1.18g...
How many moles of potassium chloride must be added to the solution to completely precipitate 1.18g dissolved Ag?
How many moles of HCl must be added to 1.0 L of 1.0 M NH3(aq) to...
How many moles of HCl must be added to 1.0 L of 1.0 M NH3(aq) to make a buffer with a pH of 9.00? (pKa of NH4+ =9.25) the answer is 0.64, explain please.
How many moles of NH4Cl must be added to 100 mL of 0.1 M NH4OH solution...
How many moles of NH4Cl must be added to 100 mL of 0.1 M NH4OH solution to prevent precipitation of Mn(OH)2 when this solution is added to 100 mL of a 0.002 M solution of MnCl2? Assume no change involume on addition of NH4Cl.
Calculate the pH of 3.0 M HP Ka=6.8 x 10^-4
Calculate the pH of 3.0 M HP Ka=6.8 x 10^-4
ADVERTISEMENT
ADVERTISEMENT
ADVERTISEMENT