Question

sa solution is made by dissolving 26.42 g of (NH4)2SO4 in enough H2O to make 50.00 mL of solution. what is the molarity of the solution

Answer 1

The answer is 0.2 M.

Molarity is a measure of the concentration of solute in a solution

c = n ÷V
c - concentration of solute,
n - number of moles of solute
V - volume of solution

We know:

V = 50.00 mL = 0.05 L

c = ?

n = ?

Let's calculate concentration:

c = m/(V * Mr)

The molar mass of (NH4)2SO4 is the sum of atomic masses (Ar) of its elements):
Mr ((NH4)2SO4) = 2Ar(N) + 8 Ar(H) + Ar(S) + 4Ar(O)
                           = 2 * 14 + 8 * 1 + 32 + 4 * 16 =
                           = 28 + 8 + 32 + 64 = 
                           = 132 g/mol

c = 26.42 g/ (0.05 L * 132g /mol) =26.42 g/ 6.6 L*g/mol = 4 mol/L = 4 M

Now, calculate molarity:
c = n ÷V
n = c * V
n = 4 mol/L * 0.05 L
n = 0.2 mol