Titrations

[BenignDMD]

Any suggestions on titrations? I keep flubbing them up making stupid mistakes....if someone can explain how to do them in good old simple english, id appreciate it! Thanks

 

[dat_student]

Any suggestions on titrations? I keep flubbing them up making stupid mistakes....if someone can explain how to do them in good old simple english, id appreciate it! Thanks

Thou shalt script a specific Q.

 

[BenignDMD]

Thou shalt script a specific Q.

lol...

What volume of HCl was added if 20mL of 1M NaOH is titrated with 1M HCl to produce a pH = 2?

 

[dat_student]

lol...

What volume of HCl was added if 20mL of 1M NaOH is titrated with 1M HCl to produce a pH = 2?

20.2 ml, let me double check my calculations

 

[elz787]

i have trouble with these too, how did you come up with 20.2?

 

[dat_student]

20.2 ml, let me double check my calculations

sorry, made a mistake

You need 20.4 mL

 

[dat_student]

lol...

What volume of HCl was added if 20mL of 1M NaOH is titrated with 1M HCl to produce a pH = 2?

20.4 mL H+ - 20 mL OH- = 0.4 ml

0.4 mL * 1 M / 40.4 mL = .01 M H+

pH = -log [.01 M] = 2

 

[BenignDMD]

20.4 mL H+ - 20 mL OH- = 0.4 ml

0.4 mL * 1 M / 40.4 mL = .01 M H+

pH = -log [.01 M] = 2

where is the .01M coming from?

 

[dat_student]

where is the .01M coming from?

0.4 mL * 1 M / 40.4 mL = .01 M H+

You need 20 mL to neutralize OH-
and
0.4 ml to get pH = 2
that makes the total volume 20 + 20 + 0.4 = 40.4 mL

 

[BenignDMD]

0.4 mL * 1 M / 40.4 mL = .01 M H+

You need 20 mL to neutralize OH-
and
0.4 ml to get pH = 2
that makes the total volume 20 + 20 + 0.4 = 40.4 mL

Ok, makes sense...thanks....

What if instead of HCl you used 1M H2SO4? That disassociates into two H+ right?

 

[elz787]

can someone explain this problem as well? (it's practically the same prob): if 10 mL of 1M NaOH is titrated with 1M Hcl to a pH of 2, what volume of HCL was added?

 

[dat_student]

Ok, makes sense...thanks....

What if instead of HCl you used 1M H2SO4? That disassociates into two H+ right?

the van hoff factor for H2SO4 is 2. So, you'd need 1/2 as much.

 

[elz787]

can someone explain this problem as well? (it's practically the same prob): if 10 mL of 1M NaOH is titrated with 1M Hcl to a pH of 2, what volume of HCL was added?

nevermind , i got it. sigh.

 

[BenignDMD]

the van hoff factor for H2SO4 is 2. So, you'd need 1/2 as much.

helpful as always, thanks