How much water must be added to 500. mL of 0.200 M HCl to produce a 0.150 M solution? (Assume th

How much water must be added to 500. mL of 0.200 M HCl to...

Key Concepts

Molarity

Molarity is a measure of the concentration of a solute in a solution, defined as the number of moles of solute per liter of solution. It is crucial in preparing solutions of a desired concentration and in performing dilution calculations.

Dilution Equation

The dilution equation, represented as C?V? = C?V?, expresses the relationship between the concentrations and volumes of a solution before and after dilution. It relies on the conservation of the number of moles of solute during the process of adding solvent.

Conservation of Moles

The principle of conservation of moles states that during dilution, the number of moles of solute remains unchanged. This allows one to equate the initial moles in the concentrated solution to the moles in the diluted solution, a key step in dilution calculations.

Volume Additivity

Volume additivity is the assumption that the total volume of a solution is equal to the sum of the volumes of the individual components that are mixed. This simplifies dilution calculations by allowing the direct use of volumes in the dilution equation.

Transcript

00:01 So for this question, we have to figure out how much water has to be added to a 500 milliliter of 0 .2 -0 -0 -0 -molar hcl solution to produce a solution with a concentration of 0 .150 molars.

00:19 So first, i've written out what we are given.

00:22 Our initial conditions are on the left.

00:25 Our initial concentration is 0 .2 .00 molars and our initial volume is 500 milliliters.

00:33 And we want a concentration of 0 .150 molars.

00:38 And we are missing our final volume that is total.

00:46 And then from that final volume, we can subtract the initial volume to figure out how much water we added.

00:53 So to find our final volume, we can use the equation c1 v1 is equal to c2 v2.

01:05 Now, the reason for this is that c times v, or concentration times volume, is equal to the number of moles.

01:17 So essentially, using the equation c1b1 is equal to c2 v2, in essence we are saying that, the number of moles initially are equal to the number of moles after and that is because when we add water to dilute a solution the number of moles of the solute doesn't change so that means the number of moles of hcl is going to be the same but we're just adding more water so that's why the moles is equal before and after and we can replace the instead of writing moles initial equals moles after we can just replace that with c and v since n is equal to c times v.

02:00 So now that i've explained that, we can sub in what we have.

02:04 So our initial concentration is 0 .2 .00 molars, and our initial volume is 500 milliliters...

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