Question

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

Answer 1

The molarity of a solution after dissolving 20 grams of LiOH in 200 mL of water is calculated by first converting grams to moles, then dividing by the volume in liters, resulting in a molarity of 4.175 M.

Step-by-step explanation:

To calculate the molarity of a solution after dissolving 20 grams of LiOH (lithium hydroxide) in 200 mL of water, you follow these steps:

• First, convert the mass of LiOH to moles by using its molar mass. The molar mass of LiOH is approximately 23.95 g/mol.
• Then, divide the number of moles of LiOH by the volume of the solution in liters to get the molarity.

Here's the calculation:

1. Calculate moles of LiOH:
   20 g LiOH × (1 mol LiOH / 23.95 g LiOH) = 0.835 moles of LiOH
2. Convert the volume of water from mL to L:
   200 mL × (1 L / 1000 mL) = 0.2 L
3. Calculate the molarity:
   0.835 moles LiOH / 0.2 L = 4.175 M

The molarity of the solution is 4.175 M.

Answer 2

4.15mol/dm³

Step-by-step 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 =
`(Number of moles of LiOH)/(Volume of solution)`

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

Number of moles of LiOH =
`(mass)/(molar mass)`

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

Number of moles of LiOH =
`(20)/(24)` = 0.83mole

Note:

1000mL = 1dm³

200mL gives 0.2dm³ of the water.

Molarity =
`(0.83)/(0.2)` = 4.15mol/dm³