i have a question about finding the concentration of a substance then changing it to a percent. i check over my notes and i can't find it.

the concentration of an unkown substance is 0.831 M

and the two given substances are 4% and 5.5%
so i do not know howto calculate which one it would be

I don't think you haven't provided enough information. The molar mass would help and the density would help.

alright! thank you, you just helped me figure it out! i didn't use all the info provided properly

I'm glad it helped but after reading my response I'm surprised it would help anyone. I really messed up that sentence. Double negatives and all.

(avg. ammount of substance)

( 28.0 mL + 27.3 mL + 27.5 mL ) / 3 = 27.7 mL

HC2H3O2 + NaOH => NaC2H3O2 + HOH

n= M x L
= 0.30 M x 0.0277 L
= 0.00831 mols

unknown:NaC2H3O2:x:1mol:NaC2H3O2:/
known:NaOH:0.00831 mols:1 mol:NaOH:
x=0.00831 mol

molar mass of HC2H302:
H x 4 = 4.04
C x 2= 24.02
O x 2= 32.00
60.06g/mol

m= n x M
= (0.00831 mol) ( 60.06g/mol)
= 0.4990986 g
= 0.4990 g

c= n / v
= (0.00831 mol) / (0.010 L)
= 0.831 M

i was just wondering if i did correct calculations and if im on the right track to finding the percent of the acetic acid

I averaged the three readings and obtained 0.0276 L instead of 0.0277 L.

So that will make a little difference. Then you are ok until you get to the 0.00831/0.010 step.
If I wanted to calculate the percent of the acetic acid in the sample, I would use the grams (the previous step) and I found 0.4973. That is 0.4973 grams acetic acid in the 10 mL sample, so in 100 mL, that is 4.97%(mass/volume). I don't know if that is the percent you want or not but that is the easiest to calculate from the data you provided.

alright thank you:)

To find the concentration of the unknown substance and convert it to a percent, you will need to follow these steps:

Step 1: Determine the molar mass of the unknown substance.
The molar mass is the mass of one mole of a substance and is expressed in grams/mole.

Step 2: Calculate the percent concentration of the unknown substance.
Divide the molar mass of the unknown substance by the molar mass of the solvent (usually water), and multiply by 100 to get the percentage.

Step 3: Compare the calculated percent concentration to the given percentages.
Compare the calculated percentage to the given percentages (4% and 5.5%). The closer the calculated percentage is to one of the given percentages, the more likely it is that the substance corresponds to that concentration.

Let's now apply these steps to your specific example:

Step 1: Determine the molar mass of the unknown substance.
You haven't provided the molar mass of the unknown substance, so I can't provide the exact concentration or percentage. However, I can help you with the calculation if you provide the molar mass.

Step 2: Calculate the percent concentration of the unknown substance.
Divide the molar mass of the unknown substance by the molar mass of the solvent (e.g., water) and multiply by 100.

Step 3: Compare the calculated percent concentration to the given percentages.
Once you have calculated the percent concentration from Step 2, compare it to the given percentages (4% and 5.5%). The substance with a calculated percentage closest to the given percentages is likely the correct one.

Please provide the molar mass of the unknown substance, and I can assist you with the calculations.