IOQJS problem - 1

To find the pH, first we need to find the basicity of $\ce{H3BO3}$ .

In $\ce{H3BO3}$ , boron has vacant p-orbitals.So,it can act as lewis acid.

From the above reaction we can conclude that basicity of $\ce{H3BO3}$ is 1 and that $\ce{H+}$ ion is of heavy water.

We have 620g of $\ce{H3BO3}$ which means 10 moles of that and only 50% of $\ce{H3BO3}$ is used means only 5 moles.

Since one molecule of $\ce{H3BO3}$ produces one $\ce{H+}$ ion . So, there will be 5 moles of $\ce{H+}$ ion.

Now,weight of $\ce{H+}$ ions = Mole * atomic weight = $5*2.014=10.070~10$

Concentation of $\ce{H+}$ = $\frac{5}{50} = 10^{-1}$

So, pH=1 and answer comes out 10+1= $\boxed{11}$