# What is the concentration of chloride ion in a solution composed by mixing 447.2*mL of 0.216*mol*L^-1 NaCl, and 100.8*mL of 0.358*mol*L^-1 CaCl_2. Why would this not be applicable to a solution of PCl_3 added to water?

Sep 15, 2017

This question is very poorly proposed.....

#### Explanation:

We can assess $\left[C {l}^{-}\right]$ with respect to the sodium chloride and the calcium chloride solutions.....We cannot do so in relation to the $P C {l}_{3}$ as we will see later.....

For $N a C l$ and $C a C {l}_{2}$ we assume that the concentrations are ADDITIVE, and we use the old ratio....

$\text{concentration"="moles of solute"/"volume of solution}$

And thus $\text{moles of solute"="concentration"xx"volume}$

$\text{Moles of NaCl"=447.2xx10^-3*Lxx0.216*mol*L^-1=0.0966*mol" (i)}$

$\text{Moles of CaCl"_2=100.8xx10^-3*Lxx0.358*mol*L^-1=0.0361*mol" (ii)}$

And so we take....$\frac{\left(i\right) + 2 \times \left(i i\right)}{\text{combined volume}}$

$\left[C {l}^{-}\right] = \frac{0.169 \cdot m o l}{0.548 \cdot L} = 0.308 \cdot m o l \cdot {L}^{-} 1$....

As for the $P C {l}_{3}$, it is a fact that liquid $P C {l}_{3}$ REACTS with water to give phosphorous acid and hydrogen chloride....

$P C {l}_{3} \left(l\right) + 3 {H}_{2} O \left(l\right) \rightarrow {H}_{3} P {O}_{3} \left(a q\right) + 3 H C l \left(a q\right)$

And thus we could not have a solution of $P C {l}_{3}$ in water or in ethanol; we COULD have such a solution in petroleum ether or methylene chloride, but these solvents are insoluble in water.

This reaction between phosphorus trichloride and water is very violent and not one that I would do with these quantities.....and so the question is VERY poorly proposed....