Question

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to prepare a 100ppm chlorine sanitizing solution:
possible answers:
a) mix 2ml of household chlorine bleach with every 1l of water
b) mix 1 part household chlorine bleach to every 10 parts water
c) mix 4ml of household chlorine bleach with every 1l of water
d) none of the above
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Explanation:

Step1: Convert ppm to ratio

ppm (parts per million) means \(1\) part solute in \(10^{6}\) parts solution. For a \(100\) ppm solution, the ratio of chlorine bleach to solution is \(\frac{100}{10^{6}}=\frac{1}{10000}\). If we assume the volume of water \(V_{water}\approx V_{solution}\) (since the volume of bleach is very small compared to water), and let the volume of bleach be \(V_{bleach}\) and volume of water be \(V_{water}\), then \(\frac{V_{bleach}}{V_{water}+V_{bleach}}\approx\frac{V_{bleach}}{V_{water}}=\frac{1}{10000}\)

Step2: Analyze each option

• Option A:

If \(V_{bleach} = 2\space mL\) and \(V_{water}=1\space L = 1000\space mL\), then the ratio \(\frac{V_{bleach}}{V_{water}}=\frac{2}{1000}=\frac{1}{500}\) (not \(100\) ppm)

• Option B:

If we assume \(1\) part bleach and \(10\) parts water, the ratio \(\frac{1}{1 + 10}=\frac{1}{11}\approx0.0909\) (not \(100\) ppm)

• Option C:

If \(V_{bleach}=4\space mL\) and \(V_{water} = 1\space L=1000\space mL\), then the ratio \(\frac{V_{bleach}}{V_{water}}=\frac{4}{1000}=\frac{1}{250}\) (not \(100\) ppm)

Answer:

D. None of the above