If 22 mL of 0.137M MgCl2 is needed to completely react 15 mL of AgNO3 solution, what is the molarity of AgNO3?

The molarity of AgNO3 is 0.401 M

calculation

Step 1: write the chemical equation for reaction

MgCl2 + 2AgNO3 → Mg (No3) 2 + 2 AgCl

Step 2: calculate the moles of MgCl2

moles = molarity x volume in liters

volume in liters=22/1000 = 0.022 L

molarity = 0.137 M or 0.137 mol/L

moles is therefore = 0.137 mol/l x 0.022 L = 3.01 x10^-3 moles

Step 3: use the mole ratio to determine the moles of AgNO3

The mole ratio of MgCl2: AgNO3 is 1:2 therefore the moles of AgNo3 is

= 3.01 x 10^-3 moles x 2/1 = 6.02 x 10^-3 moles

Step 4: find the molarity of AgNO3

molarity = moles / volume in liters

volume in liters = 15/1000=0.015 L

molarity is therefore = (6.02 x 10^-3) / 0.015 = 0.401 M