While titrating NaOH in order to find it's Molar concentration, how would the following affect the molarity?

Question

If the Buret was dirty
If the Buret tip was not completely filled with NaOH when titration began
You forgot to add Phenolphthalen indicator

Answer 1

1) Contamination could cause ions to react and ruin the results. The molarity would be higher or lower depending on the charge of the contaminating ions.

2) If buret is not full and you do not record your starting volume carefully, it will appear that you used more NaOH than you actually used. This would give you a higher molarity for your unknown.

3) With no phenolphthalein indicator you don't know when the equivalence point is reached. You would add too much NaOH and get a higher molarity, or you may stop too soon and add too little NaOH which would give a lower molarity.

Answer 2

It's been a while, but I don't think any of the above would affect the actual molarity -- the molarity is the molarity.

But all three might affect your measurement of the molarity, eh?

Answer 3

If you added no indicator there would be no color change indicating the end point.