Question

calculate the molarity of MgCl2 in the following solution: 5.34 g of MgCl2 is dissolved and diluted to 214 mL of solution.

Answer 1

Ⲁⲛ⳽ⲱⲉⲅ:

$\quad\hookrightarrow\quad \sf {0.262M }$

Ⲋⲟⳑⳙⲧⳕⲟⲛ :

Molarity is used to measure the concentration of a solution , so it is also as molar concentration. It is denoted as M or Mol/L

We are given that :

• Weight of $\sf MgCl_{2}$ = 5.34g
• Volume of solution = 214 ml , or 0.214 L

The molar mass of magnesium chloride ( $\sf MgCl_{2}$ ) is 95.21 g / mol

We can calculate the molarity of the solution by dividing the number of moles of solute by volume of solvent in liter ,i.e:

$\quad\longrightarrow\quad \sf {M = \dfrac{n}{V} }$ ‎ㅤ‎ㅤ‎ㅤ⸻( 1 )

Where,

• M = molarity
• n = number of moles
• V = Volume

We can calculate the number of moles by dividing the actual mass by its molar mass ,i.e:

$\quad\longrightarrow\quad \sf { n = \dfrac{w}{m}}$‎ㅤ‎ㅤ‎ㅤ‎⸻ ( 2 )

Where,

• n = number of moles
• m = molar mass
• w = actual mass

Therefore,

$\implies\quad \tt {n =\dfrac{w}{m} }$

$\implies\quad \tt { n =\dfrac{5.35\: g}{95.21\: g /mol}}$

$\implies\quad{\pmb{ \tt {n = 0.056 mol}} }$

Putting the values in equation ( 1 ):

$\implies\quad \tt {M=\dfrac{n}{V} }$

$\implies\quad \tt { M =\dfrac{0.056\:mol}{0.214\:L}}$

$\implies\quad\underline{\pmb{ \tt { M = 0.262 \:M }}}$