The active ingredient in aspirin is acetylsalicylic acid (mw = 180.2 g/mol). an aspirin tablet was dissolved in
water and titrated with 0.100 m naoh.
part a
if the titration required 14.85 ml of naoh to reach the phenolphthalein endpoint, how many milligrams of
acetylsalicylic acid were in the tablet?

1214 mg

Explanation:

Data given

Volume of NaOH solution (V) = 14.85 mL

Molarity of NaOH solution (M) = 0.100 M NaOH.

Amount of acetylsalicylic acid = ?

Molecular weight = 180.2 g/mol

Solution:

It is a acid base titration

As equal amount of NaOH will neutralize equal amount of acetylsalicylic acid.

First find the moles of NaOH

As we know

                 M = moles of solute / 1 L x volume of solution

Rearrange and modify the above equation

                 moles of NaOH = M of NaOH x 1 L / volume of NaOH solution

Put values in above equation

                moles of NaOH = 0.100 M x 1 L / 14.85 mL

                moles of NaOH = 0.0067 moles

Now find to find the weight of acetylsalicylic acid

As

equal amount of NaOH will neutralize equal amount of acetylsalicylic acid.

                 moles of acetylsalicylic acid =  moles of NaOH (1)

As we know  

                  no. of moles = mass in g / molar mass

So,

The modified form of equation 1 will be

              mass in g / molar mass (acetylsalicylic acid) =  moles of NaOH

Put values in above equation

                  mass in g / 180.2 g/mol = 0.0067 moles

Rearrange the above equation

                mass of acetylsalicylic acid = 0.0067 moles x 180.2 g/mol

                 mass of acetylsalicylic acid = 1.214 g

Convert the grams to milligrams

1 g = 1000 milligram

So,  

1.214 g = 1214 mg

adding or remove a gaseous reactant or product changes the concentrations. if the concentration of reactant or product is increased, the system will shift away from the side in which concentration was increased (i.e. if the concentration of reactants is increased, the system will shift toward the products. if more products are added, the system will shift to form more reactants). conversely, if the concentration of reactant or product is decreased, the system will shift toward the side in which concentration was decreased (i.e. if reactants are removed, the system will shift to form more reactants. if the concentration of products is decreased, the equilibrium will shift toward the products).

explanation: