The maximum allowable concentration of Pb2+ ions in water in a local community is 1.51 x 10-8 M. Could a chemist use 2.00 mL of 0.12 M KBr solution on a 5.00 mL sample of tap water to prove through a precipitation reaction that the water supply is safe? Show all work and reasoning
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Ответ:
The water supply is not safe.
Explanation:
Ionically, the reaction is;
Pb^2+(aq) + 2Br^-(aq) > PbBr2(s)
Amount of Br^- reacted = 2/1000 * 0.12 = 2.4 * 10^-4 moles
From the reaction equation;
1 mole of Pb^2+ requires 2 moles of Br^- for complete precipitation
x moles of Pb^2+ requires 2.4 * 10^-4 moles of Br^-
x = 1 * 2.4 * 10^-4 /2
x = 1.2 * 10^-4 moles of Pb^2+
Concentration of Pb^2+ precipitated from 5ml of tap water = 1.2 * 10^-4 * 1000/5
Concentration = 2.4 * 10^-2 M
The amount of Pb^2+ found in the water is greater than the maximum allowable concentration of Pb2+ ions in water in a local community which is 1.51 x 10-8 M. Therefore, the water supply is not safe.
Ответ:
Stoichiometry measures these quantitative relationships, and is used to determine the amount of products and reactants that are produced or needed in a given reaction. Describing the quantitative relationships among substances as they participate in chemical reactions is known as reaction stoichiometry.
Explanation: