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I need this for an experiment: ca. 3 mL concentrated (15 M) aqueous ammonia solution, NH3 (from a dropping bottle.)

I have the NH4OH pictured below. How can I dilute it to get what I need? What is the formula?

Ammonia Water

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    $\begingroup$ The label is a shame, I would not buy products from such a company for serious lab work. $\endgroup$
    – Poutnik
    May 18, 2023 at 6:45

1 Answer 1

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A solution with a mass fraction of $25\ \%$ ammonia corresponds to a concentration of $c_1=13.32\ \mathrm{mol\ l^{-1}}$. So obviously you cannot dilute this solution to reach a higher concentration of $c_2=15\ \mathrm{mol\ l^{-1}}$, which corresponds to a mass fraction of $28.5\ \%$.

Depending on the experiment, however, you could simply use more of the available solution according to $$\begin{align}n_1&=n_2\\[3pt] c_1V_1&=c_2V_2\\[3pt] V_1&=\frac{c_2V_2}{c_1}\\[3pt] &=\frac{15\ \mathrm{mol\ l^{-1}}\times 3\ \mathrm{ml}}{13.32\ \mathrm{mol\ l^{-1}}}\\[3pt] &=3.4\ \mathrm{ml}\end{align}$$

Also note that the fictitious substance “ammonium hydroxide” $(\ce{NH4OH})$ with a molar mass of $35.05\ \mathrm{g\ mol^{-1}}$ (as shown on the label) does not exist.

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  • $\begingroup$ Makes sense, but can you please show me how you got 13.32 mol l−1? $\endgroup$
    – Art
    May 20, 2023 at 5:58

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