Question

What is the molarity when 20 grams of LiOH is added to 200 mL of water?​

Answer 1

Answer:

4.15mol/dm³

Explanation:

Given:

Mass of LiOH = 20g

Volume of water = 200mL

Unkown:

Molarity of the solution =?

Solution:

Molarity is defined as the number of moles of a given solute in a volume of solution.

     Molarity = $\frac{Number of moles of LiOH}{Volume of solution}$

We don't know the number of moles of LiOH,

  Number of moles of LiOH =  $\frac{mass}{molar mass}$

Molar mass of LiOH = 7 + 16 + 1 = 24g/mol

 Number of moles of LiOH = $\frac{20}{24}$ = 0.83mole

   

Note:

    1000mL = 1dm³

     200mL gives 0.2dm³ of the water.

Molarity = $\frac{0.83}{0.2}$ = 4.15mol/dm³