Question

Determine the molarity of a solution that is prepared by adding 600 mL of water to a 200 mL of 0.450 M solution of K2Cr2O7 ?

Answer 1

0.1125 M

Step-by-step explanation:

Molarity of a solution is number of moles of solute dissolved in 1 L of solution

600 mL of water is added to 200 mL of a 0.450 M solution of K₂Cr₂O₇

number of moles of K₂Cr₂O₇ remain the same but more water is added therefore volume changes making the solution more dilute

first we need to find the number of moles of K₂Cr₂O₇ already in solution

molarity = number of moles of K₂Cr₂O₇ / volume of solution

substituting values in the equation

0.450 mol/L = number of moles / 0.2 L

number of moles = 0.09 mol

there are 0.09 mol of K₂Cr₂O₇ and the new volume is 200 mL + 600 mL = 800 mL

molarity = 0.09 mol / 0.8 L

molarity = 0.1125 mol/L

new molarity is 0.1125 M