If the PH of a 0.227 M fluoroacetic acid solution is 2.03 at equilibrium you calculate the Ks

Chemistry

ScanSolve AI Answer

Answer

4.00×10−44.00 \times 10^{-4}

Step-by-step solution

4 steps
  1. Calculate the equilibrium concentration of hydrogen ions (\ceH+\ce{H+}).

    The pH is given as 2.03.
    [\ceH+]=10−pH[\ce{H+}] = 10^{-\text{pH}}
    [\ceH+]=10−2.03[\ce{H+}] = 10^{-2.03}
    [\ceH+]=0.0093325 M[\ce{H+}] = 0.0093325\ \text{M}

  2. Set up an ICE table for the dissociation of fluoroacetic acid (HA).

    Let HA represent fluoroacetic acid. The dissociation reaction is:
    \ceHA(aq)<=>H+(aq)+A−(aq)\ce{HA(aq) <=> H+(aq) + A-(aq)}

    SpeciesInitial (M)Change (M)Equilibrium (M)
    HA0.227−x-x0.227−x0.227 - x
    H+0+x+xxx
    A-0+x+xxx

    From Step 1, we know that x=[\ceH+]eq=0.0093325 Mx = [\ce{H+}]_{\text{eq}} = 0.0093325\ \text{M}.

  3. Calculate the equilibrium concentrations of all species.

    [\ceH+]eq=0.0093325 M[\ce{H+}]_{\text{eq}} = 0.0093325\ \text{M}
    [\ceA−]eq=x=0.0093325 M[\ce{A-}]_{\text{eq}} = x = 0.0093325\ \text{M}
    [\ceHA]eq=0.227−x=0.227−0.0093325=0.2176675 M[\ce{HA}]_{\text{eq}} = 0.227 - x = 0.227 - 0.0093325 = 0.2176675\ \text{M}

  4. Calculate the acid dissociation constant (KaK_a).

    The expression for KaK_a is:
    Ka=[\ceH+][\ceA−][\ceHA]K_a = \frac{[\ce{H+}][\ce{A-}]}{[\ce{HA}]}
    Substitute the equilibrium concentrations:
    Ka=(0.0093325)(0.0093325)(0.2176675)K_a = \frac{(0.0093325)(0.0093325)}{(0.2176675)}
    Ka=0.00008710550.2176675K_a = \frac{0.0000871055}{0.2176675}
    Ka=0.00040017K_a = 0.00040017

    Rounding to two significant figures based on the pH (2.03 has two decimal places, implying two significant figures in the concentration derived from it, or the initial concentration 0.227 M has 3 sig figs, so let's use 3 sig figs for the final answer).

    Ka=4.00×10−4K_a = 4.00 \times 10^{-4}

    The KaK_a for fluoroacetic acid is:
    4.00×10−44.00 \times 10^{-4}

Was this helpful?

Try one yourself

A new problem that tests the same skill.

Still stuck on this one?

Ask a follow-up, and the answer starts from this question.

Got a different question?Ask your own question