Help on titration please.

[JohnDoeDDS]

---

Members don't see this ad.

Hi guys. I once again have a question about chemistry. I have a quiz tomorrow, and I am having trouble with these two homework problems and I might have these sort of questions tomorrow.I dont have a solutions manual so I don't knowthe answer. I would really appreciate if you can help me out. Also can u please show ur calculations for questions 2, thank you.


1) A student used 20 ml of 10% pottasium iodide rather than 15ml of 10% potassium iodide. What is the effect of this increase in potassium iodide on the calculated %NaOCl in bleach?

2) Calculate the mass of Na2S2O3(dot)5H2O needed to prepare 250 ml of .2 M solution; Include the 5 waters in your calculation of the formula mass.

For quesiton 2 this is what I did.:
M=moles/L
.2=moles/.025
moles=.005

.005*(46+64+48+90)= 1.24 grams. Does any1 know if this is right? also Im haivng trouble understanding question 1. Thanks guys.

 

[g3k]

Hi guys. I once again have a question about chemistry. I have a quiz tomorrow, and I am having trouble with these two homework problems and I might have these sort of questions tomorrow.I dont have a solutions manual so I don't knowthe answer. I would really appreciate if you can help me out. Also can u please show ur calculations for questions 2, thank you.


1) A student used 20 ml of 10% pottasium iodide rather than 15ml of 10% potassium iodide. What is the effect of this increase in potassium iodide on the calculated %NaOCl in bleach?

2) Calculate the mass of Na2S2O3(dot)5H2O needed to prepare 250 ml of .2 M solution; Include the 5 waters in your calculation of the formula mass.

For quesiton 2 this is what I did.:
M=moles/L
.2=moles/.025
moles=.005

.005*(46+64+48+90)= 1.24 grams. Does any1 know if this is right? also Im haivng trouble understanding question 1. Thanks guys.

I am not sure if my answers are right,

1) Nil. Because NaOCl is the limiting reactant and the mass ok KI doesnt matter. The data observed during weighing by difference will be different, however, the results will not vary.

2) I think what you did is right.

I amnt sure. Hopefully someone verifies this!!

 

[drat]

I am not sure if my answers are right,

1) Nil. Because NaOCl is the limiting reactant and the mass ok KI doesnt matter. The data observed during weighing by difference will be different, however, the results will not vary.

2) I think what you did is right.

I amnt sure. Hopefully someone verifies this!!

Now I'm going to admit that I, too, don't get what is being asked in #1. 😳 I think it's a titration problem so adding more KI to NaOCl will reduce the % of NaOCl in sol'n.

Your thinking is correct for #2, and assuming you plugged in the right numbers, your answer should be correct.