Sapling Learning An unknown amount of a compound with a molecular mass of 278.91

Question

Sapling Learning An unknown amount of a compound with a molecular mass of 278.91 volumetric flask. A 1.00-mL aliquot of this solution is transferred to a 25-mL volumetric flask and enou water is added to dilute to the mark. The absorbance of this diluted cm cuvette. The molar absorptivity for this compound at 343 nm is e343 = 6259 M-1 cm-1 is dissolved in a 10-mL at 343 nm is 0.548 in a 1 (a) What is the concentration of the compound in the cuvette? Number (b) What is the concentration of the compound in the 10-mL flask? (c) How many imilligrams of compound were used to make the 10-mL solution? mg Hint

Explanation / Answer

a)   A=ebc

Where A = Absorbance

e = molar absorptivity coefficient

C = concentration

b = path length,

On rearranging, we get

  c=A/eb

Putting the respective values,
c=0.548 / (6259 x 1)
c= 8.75 x 10^-5

  

b) using relation,

c1v1=c2v2

Where c1, c2 = initial and final concentration

V1, V2 = initial and final volumes

Putting the respective values, we get
c1(1.00mL)=(8. 75 x 10^-5)(10.00ml)

c1 = 8.75 x 10^-5 M

Hence, concentration of the compound in 10 mL flask is

8.75 x 10^-5 M.

c) using molarity relation,

Molarity = number of moles / volume of solution in litres

Molarity=( mass / molar mass) / volume of solution in litres

8.75 x 10^-5 M = (mass / 278.91) / 0.01 litres

8.75 x 10-7 M = mass / 278.91

2.44 x 10^-4 g = mass

0.24 x 10^-3 g = mass

0.24 mg = mass

Hence, 0.24 mg of the compound were used tk make the 10 mL solution.

  

Related Questions

Navigate

• Browse (All)
• Browse S
• Subjects

---

---

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