Question

If is found that 24.68 mL of .1165 M NaOH is needed to titrate .2931 g of an unknown acid to the phenolphthalein end point. Calculate the equivlanet mass of the acid.

Answer 1

Answer: The equivalent mass of the acid is 83.16 grams

Step-by-step explanation:

To calculate the number of moles for given molarity, we use the equation:

`\text{Moles of solute}={\text{Molarity of the solution}}*{\text{Volume of solution (in L)}}`

Molarity of
`NaOH` solution = 0.1165 M

Volume of
`NaOH` solution = 24.68 mL = 0.02468 L

Putting values in equation 1, we get:

`\text{Moles of} NaOH={0.1165M}*{0.02468L}=2.875* 10^(-3)moles=2.875* 10^(-3)geq`

( as acidity of NaOH is 1)

For end point: gram equivalents of acid = gram equivalents of base =
`2.875* 10^(-3)`

Mass of acid=
`gram equivalents* {\text {Equivalent mass}}`

`0.2391=2.875* 10^(-3)* {\text {Equivalent mass}}`

`{\text {Equivalent mass}}=83.16g`

Thus equivalent mass of the acid is 83.16 grams