Question

The osmotic pressure of a potassium chloride solution (at 300K) is 50 atmospheres.

What is the molar concentration of potassium chloride in this solution?​

Answer 1

Given:

• Osmotic pressure(π) = 50 atm
• Temperature(T) = 300 K

To find:

• Molar concentration(C)

Solution:

Vant Hoff's equation

$\dag \: \boxed{\sf{\bf{\pi V = nRT}}}$

here,

• π = osmotic pressure in atm
• V = volume in litres
• n = moles
• R = universal gas constant = 0.082 L atm / K mol

• T = Temperature in Kelvin

On rearranging,

π = (n/V)RT

we know that,

• Molar concentration(C) = n / V

Hence,

π = CRT

or

π = iCRT

here,

• i = n - factor ( no of ions )

In this case, the n-factor of the solution will be 2 ( as KCl dissociates into 2 ions K⁺ and OH⁻)

Now let's substitute the given values,

⇒ 50 = 2 x C x 0.082 x 300

⇒ C = 50 / 2 x 0.082 x 300

⇒ C = 50 / 49.2

⇒ C = 1.016 M

The molar concentration of potassium chloride in this solution is 1.016 M.