Is barium sulfate soluble in dilute mineral acid?

I have read that $\ce{BaSO4}$ is soluble in $\ce{HCl}$ , but I am not sure whether this works for dilute acid as well.


The reaction is -
$\ce{BaSO4 + 2 HCl ->BaCl2 + H2SO4}$




The key point is to have an acid with such a high $\ce{H+}$ activity that in large extent shifts the below reaction to the left :
$$\ce{ HSO4- + H2O <=> SO4^2- + H3O+ } \\ K\_\mathrm{a2}=1.0 \cdot 10^{-2}$$


Then activity of sulphate ions from dissolution of $\ce{BaSO4}$ is decreased by the equilibrium reaction and the solubility increases.


$$\begin{align}
K\_\mathrm{s}&=a\_{\ce{Ba^2+}}\cdot a\_{\ce{SO4^2-}}=1.1\times 10^{-10}\\
\frac{K\_\mathrm{a2}}{a\_{\ce{H+}}}&=\frac{a\_{\ce{SO4^2-}}}{a\_{\ce{HSO4^-}}}\\
\end{align}$$


The effective solubility product 
$$K\_\mathrm{s,ef}=K\_\mathrm{s} \cdot \frac{a\_{\ce{H+}}}{K\_\mathrm{a2}}$$


Note that despite [activity coefficients](https://en.wikipedia.org/wiki/Activity_coefficient?wprov=sfla1) {gamma} decrease with increasing ionic strength, for concentrated acids this tendency reverses and [raises very rapidly](https://chem.libretexts.org/Bookshelves/General_Chemistry/Book%3A_Chem1_(Lower)/13%3A_Acid-Base_Equilibria/11.2%3A_Strong_Monoprotic_Acids_and_Bases)



```
[HCl]  Gamma
0.0005 0.975
0.01 0.904
0.1 0.796
1 0.809
2 1.01
5 2.38
10 10.44
12 17.25

```

Therefore, $a\_{\ce{H+}}$ of 10 M HCl = 104.4.


$$K\_\mathrm{s,ef}=K\_\mathrm{s} \cdot \frac{104.4}{K\_\mathrm{a2}}\\=1.1\cdot 10^{-10}\cdot 1.044\cdot 10^4=1.148\cdot 10^{-6} \mathrm{~ mol^2 L^{-2}}$$


Solubility would be then $ M \cdot \sqrt{K\_\mathrm{s,ef}}=233.4 \cdot 0.001072=0.25\mathrm{~g/L}$


Conclusion: The $\ce{BaSO4}$ solubility in concentrated $\ce{HCl}$ is limited, in diluted one is very low. The solubility in concentrated sulphuric acid would be much higher, as $a\_{\ce{H+}}$ would be very high.


 2