The pesticide DDT (C14H9Cl5)... Express these concentrations in ppm and in milimoles per liter.
Orchard - Sample size: 250.0mL Mass of DDT: 0.030 mg
Residential - Sample size: 1.750 L Mass of DDT: 0.035 mg
Residential After a Storm - Sample size: 50.0 mL Mass of DDT: 0.57 mg
Answers are: Orchard: 1.2 x 10^-7 ppm, 3.4 x 10^-4 mmol/L; Residential: 2.0 x 10^-8, 5.6 x 10^-5 mmol/L; After-storm: 1.1 x 10^-5 ppm, 3.2 x 10^-2 mmol/L
I used the ppm formula but I'm not getting the answers the textbook is stating
molemass C14H9Cl5: 12*14+9+35*5 =352
Orchard: 4*.030E-3/352E3== 3.40909091e-10
After storm: (.57E-3)/352E3 * 1/50E-6
= 3.23863636e-6 millimole/liter
Thank You. Where do you get the 4 from the orchard calculation? And how I would figure out the ppm?
the four is from the volume, you had only 1/4 liter...so four times as much ddt per liter.
ppm? I have no clue, because you cant convert the volume to particles of something else. If you knew what the other ingredents were, you could do it.
To calculate the concentration in parts per million (ppm) and millimoles per liter (mmol/L), we need to use the following formulas:
ppm = (mass of solute / volume of solution) * 10^6
mmol/L = (mass of solute / molar mass) / (volume of solution / 1000)
Let's calculate the concentrations step by step:
1. Orchard:
Mass of DDT = 0.030 mg
Sample size = 250.0 mL
For ppm:
ppm = (0.030 mg / 250.0 mL) * 10^6
= (0.030 mg / 0.250 L) * 10^6
= 120,000 ppm
However, the textbook answer is 1.2 x 10^-7 ppm, so there may be an error in the calculation.
For mmol/L:
Molar mass of DDT = 354.49 g/mol
mmol/L = (0.030 mg / 354.49 g/mol) / (0.250 L / 1000)
= 0.085 mmol/L
The textbook answer is 3.4 x 10^-4 mmol/L, so there may be an error in the calculation.
2. Residential:
Mass of DDT = 0.035 mg
Sample size = 1.750 L
For ppm:
ppm = (0.035 mg / 1.750 L) * 10^6
= (0.035 mg / 1750 mL) * 10^6
= 20 ppm
However, the textbook answer is 2.0 x 10^-8 ppm, so there may be an error in the calculation.
For mmol/L:
mmol/L = (0.035 mg / 354.49 g/mol) / (1.750 L / 1000)
= 0.056 mmol/L
The textbook answer is 5.6 x 10^-5 mmol/L, so there may be an error in the calculation.
3. Residential After a Storm:
Mass of DDT = 0.57 mg
Sample size = 50.0 mL
For ppm:
ppm = (0.57 mg / 50.0 mL) * 10^6
= (0.57 mg / 0.050 L) * 10^6
= 11,400 ppm
However, the textbook answer is 1.1 x 10^-5 ppm, so there may be an error in the calculation.
For mmol/L:
mmol/L = (0.57 mg / 354.49 g/mol) / (0.050 L / 1000)
= 3.22 mmol/L
The textbook answer is 3.2 x 10^-2 mmol/L, so there may be an error in the calculation.
Make sure you double-check your calculations and units to ensure accuracy. In case there is an error in the textbook answer, it's always a good idea to consult with your instructor or a reliable resource for clarification.