Question

what is the concentration in ppm of selenium if 1.3 milligrams is found in 2500 kg of soil?
5.2 ppm
0.00052 ppm
52 ppm
0.0052 ppm
question 26
1 pts
what is the concentration in ppb of selenium if 1.3 milligrams is found in 2500 kg of soil?
0.52 ppb
520 ppb
5.2 ppb
0.052 ppb

Explanation:

Step1: Convert mass units to same unit

First, convert 2500 kg of soil to milligrams. Since 1 kg = 1000000 mg, then 2500 kg = 2500×1000000 = 2500000000 mg.

Step2: Calculate ppm concentration

The formula for parts - per - million (ppm) is $\text{ppm}=\frac{\text{mass of solute (mg)}}{\text{mass of solution (mg)}}\times10^{6}$. Here, the mass of solute (selenium) is 1.3 mg and the mass of solution (soil) is 2500000000 mg. So, $\text{ppm}=\frac{1.3}{2500000000}\times10^{6}=\frac{1.3\times10^{6}}{2500000000}= 0.00052$ ppm.

Step3: Calculate ppb concentration

The formula for parts - per - billion (ppb) is $\text{ppb}=\frac{\text{mass of solute (mg)}}{\text{mass of solution (mg)}}\times10^{9}$. Using the same values of solute mass (1.3 mg) and solution mass (2500000000 mg), we get $\text{ppb}=\frac{1.3}{2500000000}\times10^{9}=\frac{1.3\times10^{9}}{2500000000}=0.52$ ppb.

Answer:

Question 1: B. 0.00052 ppm
Question 2: A. 0.52 ppb