[Maciejczyk]

Hey guys,
This is first titration tasks I have been given.

Consider the chemical reaction:
HCl + NaOH → NaCl + H2O
1 mol of HCl will react with 1 mol of NaOH to form a neutral solution of salt
25ml of a solution of NaOH of unknown concentration is titrated against a standard solution of 0.5M HCl.  The initial reading of the burette is 1.05 ml and the final reading of the burette is 21.05ml.

1) What is the titre? 20ml

2) How many moles of HCl were present in the titre? 0.01

3) Therefore how many moles of NaOH are present in 25ml of the unknown solution?

4) What is the molar concentration of the unknown NaOH solution?

5) How many grams of NaOH (Mr = 40) are required to make 1L of a 0.4M solution?

6)A concentration expressed as percentage mass by volume(%m/v)is the number of grams dissolved in 100ml of solution.  What then is the %m/v concentration of NaOH in the 0.4M solution of NaOH?

As at the moment I am trying to comprehend Titration case, can I ask you to explain how to do those tasks given above so I can use them as an example? Thank you!

[Arkcon]

Surely you remember, from your other thread, that we don't dump complete answers on this forum.  You've filled in some basic information, but can you use it to start figuring out the next step?  You've called this titration, but the problem is the same as your last one:  How to relate moles and molarity and grams and volumes.  For example:

5) How many grams of NaOH (Mr = 40) are required to make 1L of a 0.4M solution?

Is this in any significant way different from this other entire thread?

http://www.chemicalforums.com/index.php?topic=66003.0

[Maciejczyk]

You are right. I try not to make that mistake. However, I have figured out tasks 1,2 and 5.

I am just stuck on 3,4 and 6. I have no idea how to do it.

[sjb]

For 3, what does HCl + NaOH → NaCl + H₂O mean?

[Borek]

Note: "task" doesn't mean what you think. In English it is either "question" or "problem".

[Maciejczyk]

For 3, what does HCl + NaOH → NaCl + H₂O mean?

I don't know.