Calculating Mass of Acid in Vinegar

[majinknight]

Hello this is my question. Ok I need to find the molar mass of acetic acid and then calculate the mass of acid in the volume of vinegar I used. Now the equation for the lab i did was
CH3COOH + NaOH produces NaCH3COO + H20

The information I have is that the concentration of the sodium hydroxide is 0.20 mol/L, the volume of sodium hydroxide is 79mL, the volume of acetic acid I used was 25mL, I calculated the number of moles use in the sodium hydroxide and it was 0.0158 mol and since everything is on a 1 to 1 basis the number of moles for the acetic acid is 0.0158mol. From that I calculated the number of moles of acetic acid and it is 0.632 mol/L. I calculated the molar mass of the acetic acid by taking the 0.0158 mol of CH3COOH x 60g (the weight of the acid) which got me an answer of 0.948 grams. Now what I do not understand is how to calculate the mass of acid in the volume of vinegar. I may have everything to answer the question here but i just don't know what to do.

Plz Help me!

 

[Monique]

Originally posted by majinknight
Hello this is my question. Ok I need to find the molar mass of acetic acid and then calculate the mass of acid in the volume of vinegar I used. Now the equation for the lab i did was
CH3COOH + NaOH produces NaCH3COO + H20

Hi Majinknight! Welcome to the forums!

So to summarize: You neutralized 25 ml of CH₃COOH with 79 ml of NaOH [0.20 mol/l]

You calculated the number of moles of CH₃COOH in your solution: 79 * 0.20*10^-3 = 0.0158. You do not have to calculate the concentration of the CH₃COOH!

Next, you calculated molar mass of CH₃COOH, you do not explain how you did that? I can do it out of my head: the molar mass of C=12, O=16, H=1. Combine that and CH₃COOH = 60 grams per mole.

Without knowing it you already answered your own question: "Now what I do not understand is how to calculate the mass of acid in the volume of vinegar".

You multiplied the molar mass of CH₃COOH with the number of moles in the volume and that is your answer: 0.0158 * 60 = 0.948 g.

 

[majinknight]

Oh really the question said find the molar mass of acetic acid. Then calculate the mass of acid in the volume of vinegar. I thought that the molar mass of acetic acid was 0.948g, but the molar mass is just the 60grams. Ok Thank You so much.

 

[Monique]

Yes, the molar mass (m_w) is the mass of a mole of a substance