# Question #c644d

Jun 10, 2016

If $x = y$, then the expression $y = x$ is also valid.
Proof.
$x = y$, taking $x$ to RHS and $y$ to LHS we obtain
$- y = - x$, Dividing both sides with $- 1$, we obtain
$y = x$
$40 m L$

#### Explanation:

Using the mole conservation equation
moles before dilution$=$moles after dilution
(we can also write moles after dilution$=$moles before dilution)
or ${M}_{1} {V}_{1} = {M}_{2} {V}_{2}$
$0.250 \text{mol"/"L"xxV_1=0.100"mol"/"L} \times 100.0$
or ${V}_{1} = \frac{0.100 \times 100}{0.250}$
or ${V}_{1} = 40 m L$