In this experiment a Shimadzu TOC-V_CPH is employed. The TOC-V_CPH measures orga

Question

In this experiment a Shimadzu TOC-V_CPH is employed. The TOC-V_CPH measures organic carbon by oxidative combustion. The sample is introduced into a combustion tube filled with an oxidative catalyst and heated to 680 degree C. The resulting CO_2 is measured in a non-dispersive infrared NDIR detector by monitoring the IR bands corresponding to the C-O bond stretch. The NDIR detector outputs an analog detection signal which will form peaks as CO_2 is detected. These peaks in be integrated and the resulting peak area is proportional to sample carbon concentration by Lambert's Law. The TOC-V_CPH is also capable of on-line sample acidification and purging directly determine TOC. This process is referred to in the instrument literature and control software as NPOC, for non-purgeable organic carbon. Pre-Lab Questions Potassium Hydrogen Phthalate (KHP, C_8H_5KO_4 F.W.=204.2236 g/mol) is the carbon source for the standards in this experiment. Calculate the mass of KHP required to make a 250 ppm C solution in a 250 mL volumetric flask. Calculate the volumes required to make five 100 mL standards from the 250 ppm C stock solution. The five standards are equally spaced over the range of 0 to 20 ppm C.

Explanation / Answer

(1)

We know:

1 ppm = 1 mg/L

To make 250 ppm solution in C, we need: 250 mg/L C in the solution

Since the solution volume should be 250 mL, this means that mass of C in the solution should be: 250/4 = 62.5 mg = 0.0625 g

Moles of C in this much mass = 0.0625/12 = 0.0052

Now, 1 mole KHP gives 8 moles C

Thus moles of KHP required = 0.000651

So, mass of KHP required = 0.000651 * 204.2236 = 0.133 g

(2)

For standard 1 with conc 0 ppm:

Add 0 mL stock and 100 mL distilled water

For standard 2 with conc 5 ppm:

Add 2 mL stock and 98 mL distilled water

For standard 3 with conc 10 ppm:

Add 4 mL stock and 96 mL distilled water

For standard 4 with conc 15 ppm:

Add 59.8 mL stock and 40.2 mL distilled water

For standard 5 with conc 20 ppm:

Add 8 mL stock and 92 mL distilled water

Related Questions

Navigate

• Browse (All)
• Browse I
• Subjects

---

---

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