Question

Scenario 3: In small amounts (-1 ppm = 1 mg/L) copper (II) ions are used as an algaecide in swimming pools. Blue Water Pool Treatments (BWPT), a producer of algaecide and other pool chemicals, recently had an incident at one of their manufacturing plants; someone added too much copper sulphate to the product mixture, resulting in an algaecide that is more concentrated than the labelling (and usage instructions) indicate. The remedy of course is to dilute the product mixture, but to do so, BWPT must first determine the current Cu2+ concentration in their defective product. Your task is to analyze the copper algaecide solution answer the following questions: 1. How much Cu2+ ion is present in the test solution in moles/L? 2. The labelling on the product bottle gives the instruction to "use 1 mL of product per L of pool water". Using this ratio, calculate the concentration of Cu2+ that the product must have to achieve the desired 1 ppm Cu2+. 3. What amount of solvent (a proprietary blend of hydrogen and oxygen) must be added to each litre of defective product to reach this concentration? 46

Test sample volume = 10.00 mL
Average NaOH volume = 13.10
NaOH concentration = 0.1051 M

Answer 1

1a) First of all we want to convert Cu ions concentration to grams per litre

Cu ions concentration = 1ppm = 1mg/L = 1$\times$10^-3 g/L

Gram molecular mass of Cu²⁺ =63.54g

no.of moles of Cu²⁺ in 1$\times$10^-3 g = 1$\times$10^-3 g $\div$ 63.54g

=15.75$\times$10^-6 mol

so the test solution contains 15.75$\times$10^-6 moles/L of Cu²⁺ ions . Here the test sample is 10ml ie; .01L

So now the 10 ml of test solution contains .01$\times$ 15.75$\times$10^-6 mol of Cu²⁺

= 15.75$\times$10^-8moles