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17 July, 00:56

When blood is donated, sodium oxalate solution is used to precipitate Ca2+, which triggers clotting. A 122.0-mL sample of blood contains 9.70 * 10-5 g Ca2+/mL. A technologist treats the sample with 100.0 mL of 0.1550 M Na2C2O4. Calculate [Ca2+] after the treatment. (CaC2O4 · H2O Ksp = 2.30 * 10-9) Enter your answer in scientific notation.

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  1. 17 July, 04:54
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    [Ca2+] = 3.36 * 10^-8 M

    Explanation:

    Step 1: Data given

    A 122.0-mL sample of blood contains 9.70 * 10^-5 g Ca2+/mL.

    A technologist treats the sample with 100.0 mL of 0.1550 M Na2C2O4.

    Ksp = 2.30 * 10^-9

    Step 2: Calculate mass of Ca2+

    Mass Ca2 + = 9.70 * 10^-5 g Ca2+/mL * 122 mL

    Mass Ca2 + = 0.011834 grams

    Step 3: Calculate moles of Ca2+

    Moles Ca2 + = mass Ca2 + / molar mass Ca2+

    Moles Ca2 + = 0.011834 grams / 40.078 g/mol

    Moles Ca2 + = 2.95 * 10^-4 moles = 0.000295

    Step 4: Calculate moles of C2O4^2-

    Moles C2O4^2 - = Molarity * volume

    Moles C2O4^2 - = 0.1550 M * 0.100 L

    Moles C2O4^2 - = 0.0155 moles

    Step 5: Calculate limiting reactant

    Ca2 + is the limiting reactant. It will completely be consumed (0.000295 moles).

    C2O4^2 - is in excess. There will 0.000295 moles be consumed. There will remain 0.0155 - 0.000295 = 0.015205 moles of C2O4^2-

    Step 6: Calculate total volume

    Total volume = 122.0 mL + 100.0 mL = 222.0 mL = 0.222 L

    Step 7: Calculate concentration CaC2O4

    [CaC2O4] = 0.000295 mol / 0.222 L

    [CaC2O4] = 0.00133 M

    Step 8: Calculate concentration of C2O4^2-

    [C2O4^2-] = 0.015205 mol / 0.222L

    [C2O4^2-] = 0.0685 M

    Step 9: Calculate [Ca2+]

    Ksp = 2.3 * 10^-9 = [Ca2+] [C2O42-]

    2.3 * 10^-9 = X * (X+0.0685)

    X = [Ca2+] = 3.36 * 10^-8 M
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