If 87 grams blah blah blah...

Question

10. If 87 grams of K2SO4 (molar mass 174 grams) is dissolved in enough water to make 250 milliliters of solution. what are the concentrations of the potassium and the sulfate ions?

Answer 1

Moles K2SO4 = 87 g/ 174 g/mol = 0.50

K2SO4 is a strong salt :

K2SO4 >> 2 K+ + SO42-

Moles K+ = 0.50 x 2 = 1.0

[K+] = 1.0 mol / 0.250 L =4.0 M

moles SO42- = 0.50

[SO42-] = 0.50 mol / 0.250 L =2.0 M