Chemistry Help Please?

👨🏻‍🏫 學術台化學

[匿名]

2020-11-02 6:15 am

If I have 100mM KCL
and I am trying to find the Log10 value for K+ ions
because the ratio of K:CL is 1:1
does that mean this equation would be correct? Log10(100/2)?Or would it be just Log10(100)?

更新1:

Hey @ Roger, Thank you for your answer :) I understand where I have gone wrong in the first equation, by / by 2 I don't understand why using 0.1M instead of 100mM would make a huge difference, please could you explain why do Log10(100x10^3) instead of Log10(100)? Thank you :)

回答 (1)

Roger the Mole

2020-11-02 6:40 am

Neither of your answers. You're ignoring the initial "m" in "100mM".

It would be:
Log10(100 × 10^-3)

You do not divide by 2. The concentration of K{+} ions is the same as the concentration of KCl because there is an equal number of moles of KCl and K{+}:
KCl → K{+} + Cl{-}
and the KCl dissociates completely.

It does not matter what the ratio is between K and Cl. You are not interested in the Cl.
What's important is the ratio of KCl to K{+}.

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