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Gen. Chem Question

Discussion in 'MCAT Study Question Q&A' started by vanillabear55, Oct 29, 2014.

  1. vanillabear55

    vanillabear55 just keep swimming 7+ Year Member

    645
    102
    Feb 23, 2009
    Which of the following is required to neutralize 5.00 mL of 0.20 M CaCO3 (aq)?

    A. 10.0 mL 0.10 N NaOH(aq)
    B. 10.0 mL 0.10 N HNO3 (aq)
    C. 10.0 mL 0.30 N H3PO4 (aq)
    D. 10.0 mL 0.20 N HCl (aq)

    Explanation too please, so confused.

    Thanks!
     
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  3. Hadi7183

    Hadi7183 2+ Year Member

    63
    22
    Dec 8, 2013
    NWT
    The answer is D. CaCO3 is dissociated (not really - see below) to Ca2+ and (CO3)2-, which can be considered as a Bronsted-Lowry base and is neutralized by two equivalents of H+. Since you have 5mL*0.2M=1mmol of (Co3)2-, you need 2 mmol of H+, which is the HCl solution in D. The final products are CaCl2 and H20+CO2 (H2CO3).

    Keep in mind that CaCO3 is NOT soluble in water, but it can react and get dissolved by a strong acidic solution (e.g., HCl).
     
    vanillabear55 likes this.

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