Today I determined the concentration of my existing nitric acid via titration using sodium hydroxide. I ended up determining the concentration to be roughly 59% by weight.
Procedure:
I first determined the rough amount of NaOH I’d need to complete the titration using the following stoichiometry:
NaOH + HNO 3 → NaNO 3 + H 2 O
Which gave me a bit less than 5 grams of NaOH to neutralize 5ml of 68% nitric acid. I then prepared a solution with exactly 4.76g NaOH and 74.23g of Water giving me a total weight (including beaker and pipette) of 147.33g. I then measured out 2.5ml of nitric acid into another beaker and diluted it with an arbitrary amount of water. I added a bit less than half of the NaOH solution over 3 additions until I got a basic reading using PH paper for a total addition of 26.27g of NaOH solution. I did a repeated run, estimating that I’d need roughly 24g of NaOH solution. I added in 23.12g of NaOH solution over 4 additions which gave me a slightly acidic reading using PH paper. I did one final adition of 0.35g of NaOH solution which gave me a total addition of 23.47g of solution and a slightly basic reading with PH paper. Using the second run, I determined the Molarity of my nitric acid to be ~14.1M giving me a final calculated concentration of 59.2% w/w.