Question

Calculate the molarity a solution that is obtained by dissolving 20 g of KCl in enough water to obtain 355 mL of the solution. Assume the molar mass of KCI is 74.6 g/mol (14) is 63.0 g/mol. * (3 pts) Calculate the molality of HNO, solution that is 24% by mass. Assume the molar mass of HNO

Answer 1

a) Molarity KCl = 0.755 M

b) molality HNO = 5.09 m

Step-by-step explanation:

• Formality (F) = moles sto / L sln
• Molarity (M) = # dissolved specie / L sln
• molality (m) = moles sto / Kg ste
• %p/p = ( g sto / g ste ) * 100

a) KCl ↔ K+ + Cl-

moles KCL:

⇒ 20 g KCl * ( mol / 74.6 g ) = 0.268 mol KCl

⇒ F = 0.268 mol KCl / 0.355 L = 0.755 F

⇒ M [ K+ ] = 1 * ( 0.755) = 0.755 M

b) 24% HNO:

calculation base: 1 g solution:

⇒24 = ( g sto / g sln) * 100

⇒ 0.24 = g sto / 1

⇒ g sto = 0.24g

⇒g sln = 1 - 0.24 = 076g sln

⇒Kg ste = 0.76 g * ( Kg / 1000g ) = 7.6 E-4 Kg ste

moles sto (HNO):

⇒ 0.24g * ( mol / 62.03g) = 3.869 E-3 moles HNO

⇒ m = 3.869 E-3 moles HNO / 7.6 E-4 Kg sln

⇒ m = 5.09 mol/Kg