Question

You dissolve 4.5 mol of potassium hydroxide to make a 2 L solution. What is the molarity of the solution?

Answer 1

Data:
M (molarity) = ? (Mol/L)
m (mass) = ? (in grams)
V (volume) = 2 L
MM (Molar Mass) of Potassium Hydroxide (KOH)
K = 1*39 = 39 amu
O = 1*16 = 16 amu
H = 1*1 = 1 amu
------------------------------------
MM of KOH = 39+16+1 = 56 g/mol

***Let's find the mass
Data:
n (number of mols) = 4.5 mols
m (mass) = ? (in grams)
v (volume) = 2 L

Formula:


`n = (m)/(V)`

`4.5 = (m)/(2)`

`m = 4.5*2`

`\boxed{m = 9.0\:g}`

***Let's find the molarity:

Formula:


`M = (m)/(MM*V)`

Solving:

`M = (m)/(MM*V)`

`M = (9.0)/(56*2)`

`M = (9.0)/(112)`

`M = 0.0803...\:\to\:\boxed{\boxed{M \approx 0.08\:Mol/L}}\end{array}}\qquad\quad\checkmark`