Boron trichloride (117.16 g/mol) of mass 23.43 g is poured into water: BCl₃ + 3H₂O → B(OH)₃ + 3HCl…

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Boron trichloride ( $117.16\ \text{g/mol}$ ) of mass $23.43\ \text{g}$ is poured into water: $\text{BCl}_{3} + 3\text{H}_{2}\text{O} \to \text{B}(\text{OH})_{3} + 3\text{HCl}$ . The molar masses are $36.46\ \text{g/mol}$ for HCl and $61.83\ \text{g/mol}$ for boric acid. Find the mass of hydrogen chloride that forms, the mass of boric acid and the pH if the products make $1.00\ \text{L}$ of solution. Treat HCl as a strong acid and ignore the weak acid.

Need a reminder? The key ideaShow

Each Cl of a chloride that is hydrolysed ends as one HCl, and HCl is a strong acid, so $[\text{H}^+]$ equals the moles of HCl for each litre. A gas at $273\ \text{K}$ and $1\ \text{atm}$ has a molar volume of $22.4\ \text{L/mol}$ . Magnesium silicide and acid give silane, $\text{Mg}_{2}\text{Si} + 4\text{HCl} \to 2\text{MgCl}_{2} + \text{SiH}_{4}$ . Lithium aluminium hydride and water give four moles of hydrogen for each mole.

The worked solution

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Work it out on paper first. It is fine to get stuck or make a mistake: that is how we learn. When you are ready, go through the solution one step at a time, and check each step against your own.

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