What is the molarity of a solution made by mixing 200 mills of pure water with 100 MLS of 0.75 molar potassium chloride solution? All right, so anytime we're adding water to any type of solution, that means that we are doing a dilution. So remember a dilution is anytime we're adding, mixing or titrating with water. And when it comes to dilution, we use the dilution formula which is M1V1=M2V2.
So they're asking us what is the molarity after we've added this water. So they're asking me what is M2? The word of means multiply, which makes sense because this would be my M1. This would be my V1. They're multiplying each other. We don't know what M2 is now. V2 equals our final volume and our final volume equals the volume initially that we had plus the volume of added water.
So initially we started out with 100 MLS right here, 100 MLS. And what did we do to that 100 MLS? Well we added an additional 200 MLS of water so that mean my final volume or V2 is 300 MLS. So all we have to do now is solve for M2 so divide both sides by 300 mills so it would just be oh .75 / 3. So my new molarity would be .25 molar, giving me option B as the correct choice.
So remember in a dilution, your new concentration or molarity which is M2 is always smaller than your M1. So this is just a basic dilution question where we have to use the dilution formula. Continuing with this idea of dilution, let's see if you guys can figure out how to answer example three. Once again, if you get stuck and don't know where to go, just come back and take a look at the next example video where I go over how to approach this very question.