A stock solution was prepared by dissolving exactly 0.4000 g of pure ASA (180.16 g/mol)
in 10.00 mL of NaOH and heating the solution to a gentle boil. After cooling to room temperature, the solution was poured into a 250-mL volumetric flask and diluted to the mark with DI water. Before coming to lab, calculate the concentration of ASA in the flask.
None of the ASA is boiled away, presumably. Therefore you have 0.4000 g of ASA in 250 mL of liquid solution. With the molecular weight that was given, you can convert that to molarity (moles per liter)
To calculate the concentration of acetylsalicylic acid (ASA) in the flask, we need to consider the initial amount of ASA and the final volume of the flask.
1. Calculate the moles of ASA:
Mass of ASA = 0.4000 g
Molar mass of ASA = 180.16 g/mol
Number of moles = Mass / Molar mass
Number of moles = 0.4000 g / 180.16 g/mol
2. Calculate the concentration in the 10.00 mL solution:
Concentration (C1) = Moles / Volume
Concentration (C1) = (0.4000 g / 180.16 g/mol) / 0.0100 L
(Divide by 0.0100 L to convert mL to L)
Now, we need to consider the dilution of the solution when it is transferred to the 250 mL volumetric flask:
3. Calculate the concentration in the flask:
Concentration (C2) = Concentration of the initial solution * (Volume of initial solution / Volume of final solution)
Concentration (C2) = C1 * (10.00 mL / 250.00 mL)
(Divide by 250.00 mL to convert mL to L)
Now, let's calculate the values:
1. Calculate the moles of ASA:
Number of moles = 0.4000 g / 180.16 g/mol = 0.00222 mol
2. Calculate the concentration in the 10.00 mL solution:
Concentration (C1) = 0.00222 mol / 0.0100 L = 0.222 M
3. Calculate the concentration in the flask:
Concentration (C2) = 0.222 M * (10.00 mL / 250.00 mL) = 0.00888 M
Therefore, the concentration of ASA in the flask is 0.00888 M.