What is the volume of acid the student should measure to make the 0.1M solution?

Question

What is the volume of acid the student should measure to make the 0.1M solution?

Scroll down for mo O acetic acid, Ka 1.75x10 5, 5.00 M o formic acid, Kei 1.77x10 4.200 M o phonic acid, Ka 7.52x10-3, 1.00 M Conjugate bases. O sodium formate, HCOONa sodium dihydrogen phosphate monohydrate, NaH2PO4 H20 O sodium propionate, CH3CH20 sodium acetate trihydrate, Scroll down CH COONa. 3H20 to view more The final volume of buffer solution must be 100.00 mL and the final concentration of the weak acid must be 0.100 M, Based on this information, what mass of solid Based on this information, what volume of conjugate base should the student weigh out to acid should the student measure to make make the buffer solution with a pH 3.5 the 0.100 M buffer solution? 0.380668 g Previous 8 Give up s view solution Try Again Next H Exit

Explanation / Answer

We need to make a 100mL buffer of formic acid and sodium formate.

Gven Ka of acid = 1.77x10-4 and molarity of stock solution of acdi = 2M

In the buffer [acid] = 0.1M

ii)Volume of stock solutionof acid to be used is calculated by using V1M1 = V2 M2

Thus 100mL x 0.100M = VmL x 2M

Thus volume = 100mL x0.1M /2M = 5 mL

i) mass of solid conjugate base ,HCOONa

We know pH of buffer is calculated using Hendersen equation

pH = pKa + log [conjugate base]/[acid]

3.5 = (4-log1.77) + log (xM/0.1M)

= 3.75+ log (xM/0.1M)

Thus calculating x =0.380 g

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