Question

Calculate the molarity (M) of a solution that contains 4.0 grams of KOH and has a volume of 2.0 L.

Answer 1

Answer:

The answer to your question is 0.036 M

Explanation:

Data

Molarity = ?

mass = 4.0 grams KOH

Volume = 2 L

Molecular mass KOH = 39 + 16 + 1 = 56 g

Formula

$Molarity = \frac{moles}{volume}$

Process

1.- Calculate the moles of KOH using proportions

                       56 g of KOH ---------------- 1 mol

                         4  g of KOH ----------------  x

                         x = (4 x 1) / 56

                         x = 0.071 moles

2.- Substitute the values in the formula to find Molarity

$Molarity = \frac{0.071}{2}$

3.- Simplification and result

       Molarity = 0.036 M

Answer 2

Answer:

molarity = 0.035 M

Explanation:

We need to find moles to first in order to place in molarity's formula :

Molarity = number of moles (n)/ volume (V) ....... (1)

KOH molecular formula = M = 56

Volume = V = 2 L

mass = m = 4 g

number of moles (n) = mass (m) / molecular mass (M)

n = 4/56

n = 0.07 moles

Substituting value of n in equation (1)

Molarity = 0.07/2

Molarity = 0.035 M