ND Quiz 3 Chemistry 1128 Fall 201 Please show all work. Write your name on the b

Question

ND Quiz 3 Chemistry 1128 Fall 201 Please show all work. Write your name on the back of this page (14 points) You are given a flask containing 250.0 mL of 0.100 M acetic acid (CH COOH, K, - 1.8x 10) and a jar containing solid sodium acetate (CH COONa), molar mass 82.03 g/mol). 1. a. What mass of sodiumacetate must you add to the flask to produce a buffer with a pH of 5.25? Assume the volume does not change when the solid is added. -] 0 3.45 0.025 405x10 .025 0.32- 82.03 0.32 What is the pH of the buffer after the addition of 0.0210 mol of NaOH (assume the volume does not change with the addition)? b. 6.32 0.995 0.02(0 0,32 6.23 O, 2 0,274 0.2 46 ry

Explanation / Answer

a)

mass of acetate required to get pH = 5.25

pH = pKa + log(acetate/Acetic acid)

5.25 = 4.75 + log(acetate/Acetic acid)

(acetate/Acetic acid)= 10^(5.25-4.75) = 3.1622

(acetate/Acetic acid)= 3.1622

if acetic acid = 0.1 M

then

[Acetate] = 3.1622*0.1 = 0.31622 M

which means

mol of acetate = MV =0.31622 * 0.25 = 0.079055 mol of acetate

mass of Naac = mol*MW = 0.079055*82.03 = 6.4848 g of NaAc required

b)

pH if we add 0.021 mol of NAOH

mol of acid = MV = 0.1/0.25 = 0.025 mol of acid

mol of acetate = 0.079055

after addition

mol of acid = 0.025-0.021 = 0.004

mol of acetate = 0.079055+ 0.021 = 0.100055

pH = 4.75 + log(0.100055/0.004)

pH = 6.15

Related Questions

Navigate

• Browse (All)
• Browse N
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.