# Question b98fe

May 16, 2017
1. $1 m o l {K}^{+} , 1 m o l C {l}^{-}$
2. $1 m o l M {g}^{2 +} , 2 m o l N {O}_{3}^{-}$

#### Explanation:

In one liter of a one molar solution, the number of moles of the solute is

$\left(M\right) \left(V\right) = \left(1 \frac{m o l}{L}\right) \left(1 L\right) = 1 m o l$

For $K C l$, there are one atom of each per formula unit, so there are one mole of each ${K}^{+}$ and $C {l}^{-}$ in one liter of a $1 M$ solution of potassium chloride.

For $M g {\left(N {O}_{3}\right)}_{2}$, there are two moles of $N {O}_{3}^{-}$ per one mole of $M {g}^{2 +}$, so there is one mole of $M {g}^{2 +}$ and two moles of $N {O}_{3}^{-}$ in one liter of a $1 M$ solution of magnesium nitrate.

May 16, 2017

$K C l$: $2 m o l$
$M g {\left(N {O}_{3}\right)}_{2}$: (Approximately) $3 m o l$.

#### Explanation:

Both $K C l$ and $M g \left(N {O}_{3}\right) 2$ are salts. Thus they completely ionize when dissolved in water (to yield ${K}^{+}$, $C {l}^{-}$, $M {g}^{+ 2}$ and NO_(3)^(2-), respectively.)
The number of moles of ions produced from $K C l$ dissolving:
$1 m o l {K}^{+} + 1 m o l C {l}^{-} = 2 m o l \left(i o n s\right)$
The number of moles of ions generated from $M g \left(N {O}_{3}\right) 2$ dissolving:
$1 m o l M {g}^{2 +} + 2 m o l \left(N {O}_{3}^{-}\right) = 3 m o l \left(i o n s\right)$

However, if you take the reversible reaction into account: $M {g}^{2 +} + 2 \left(O {H}^{-}\right) r i g h t \le f t h a r p \infty n s M g \left(O H\right) 2$
K_(sp)=5.61×10−12 for $M g \left(O H\right) 2$.
Let the number of $M {g}^{2 +}$ converted in this reaction equals to $x$, using the RICE table,
(1-x)*(10^(-7)-2x)=5.61×10^(−12)#, $x = 4.99972 \cdot {10}^{-} 8$.
This value is too small to be considered.
Therefore the moles of ions in $1 L$ of $1 M$ $M g {\left(N {O}_{3}\right)}_{2}$ solution is $3 m o l$.

(reference: https://en.wikipedia.org/wiki/Magnesium_hydroxide )
[What's the meaning of the ICE table.. as seen in this equilibrium solution?],(https://socratic.org/questions/what-s-the-meaning-if-ice-table-as-seen-in-this-equilibrium-solution).