Question

an environmental chemist found 2.4 x 10^{-2}g of a pesticide in 2.00 l of water.

1. what is the % m/v?

\\_\\_1\\_\\_ g
% m/v = --------- 100% = \\_\\_2\\_\\_ % m/v
\\_\\_3\\_\\_ ml

1. what is the concentration ppm?

\\_\\_4\\_\\_ g
ppm = ---------( \\_\\_5\\_\\_ ) = \\_\\_6\\_\\_ ppm
\\_\\_7\\_\\_ ml
a. 36.00 b. 5.00 c. 31.00 d. 150.0 e. 12 f. 350.00
g. 100.0 h. 2.4 x 10^{-2} i. 1.2 x 10^{-3} j. 1.786 k. 7.143 l. 25.00
m. 7.500 n. 125.0 o. 500.0 p. 15.00 q. 185.00 r. 444.44 i
s. 2.00 x 10^{3} t. 20.67 u. 0.500 v. 499.5 w. 15 x. 33.33
y. 1.00 x 10^{5} z. 10.0 aa. 1.00 bb. 10^{6} cc. 6.00
dd. 6.00 x 10^{-5} ee. 6.00 x 10^{6} ff. 20.0 gg. 200 hh. 1.20 x 10^{6}
ii. 60 jj. 0.100 kk. 4.00 ll. 10^{3} mm. 0.0667 nn. 66.7

Explanation:

Step1: Convert liters to milliliters for % m/v

Since \(1L = 1000mL\), then \(2.00L=2.00\times1000 = 2000mL\). The mass of the pesticide is \(2.4\times10^{- 2}g\).
The formula for \(\%m/v=\frac{\text{mass of solute (g)}}{\text{volume of solution (mL)}}\times100\%\)
So, \(\%m/v=\frac{2.4\times 10^{-2}g}{2000mL}\times100\%\)

Step2: Calculate % m/v

\(\frac{2.4\times 10^{-2}}{2000}\times100=\frac{2.4\times10^{-2}\times100}{2000}=\frac{2.4}{2000}= 0.0012 = 0.12\%\)

Step3: For ppm calculation

The formula for ppm (parts per million) is \(ppm=\frac{\text{mass of solute (g)}}{\text{volume of solution (mL)}}\times10^{6}\)
We have mass of solute \(m = 2.4\times10^{-2}g\) and volume of solution \(V=2000mL\)
So \(ppm=\frac{2.4\times 10^{-2}g}{2000mL}\times10^{6}\)

Step4: Calculate ppm

\(\frac{2.4\times10^{-2}\times10^{6}}{2000}=\frac{2.4\times10^{4}}{2000}=12\)

Answer:

1. \(H\), \(JJ\), \(S\)
2. \(H\), \(BB\), \(S\), \(E\)