Question

Potassium hydrogen phosphate is used in the preparation of non-dairy powdered creamers. Calculate the molarity of a solution prepared by dissolving 238 g of K2HPO4 in enough water to produce 275 mL of solution. A) 0.732 M B) 0.865 M. C) 2.66 M D) 4.97 M E) none of the above

Answer 1

Answer:

D) 4.97M

Explanation:

firstly we will calculate the molar mass of K2HPO4.

K=39, H=1 , P=31,   O=16

K2HPO4 = (39*2)+(1)+(31)+(16*4) =174g/mol

number of moles = mass / molar mass

mass of K2HPO4 =238g

number of moles = $\frac{238}{174}$ moles.

$\frac{238}{174}$ moles is contained in 275mL of solution.

The molarity of a solution is the number of moles of solute contained in 1000mL of solution.

if  $\frac{238}{174}$ moles  is contained i 275mL of solution

Then X will be contained in 1000 mL of solution

$x=\frac{\frac{238}{174}*1000}{275}$

x=4.9739moles

x ≈ 4.97moles

4.97moles is contained in 1000mL of solution.

The molarity of the solution is 4.97M