In the laboratory you dissolve 219 g of ammonium chloride in...

In the laboratory you dissolve 21.9 g of ammonium chloride in a volumetric flask and add water to a total volume of 125 mL. What is the molarity of the solution? What is the concentration of the ammonium cation? What is the concentration of the chloride anion?

Transcript

00:02 Hi there.

00:03 In this question, we are trying to determine the molarity of the solution.

00:07 So molarity is a way to measure concentration in chemistry, and it's defined as the moles of solute per liter of solution.

00:24 So it's solute per solution.

00:26 Well, as we look at this question, we see that we have 21 .9 grams of the solute, which is ammonium chloride.

00:34 So that would have the formula nh4 for ammonium and cl for the chloro.

00:39 We have a one positive charge and a one negative charge, so we don't need any additional subscripts.

00:46 This is dissolved into solution with a total volume of 125 milliliters.

00:54 Okay, so this is a concentration, but it's not the units that we want for molarity.

00:59 For molarity, we need molarity, we need to do a little bit of converting here.

01:03 We need to convert the numerator from grams to moles, and the denominator from milliliters to liters.

01:09 So let's do one at a time.

01:11 Let's start with the numerator.

01:12 To convert from grams to moles, we need the molar mass of ammonium chloride.

01:16 So we need to add together the mass of one nitrogen, four hydrogens, and one chlorine.

01:22 That gives us a mass of 53 .50 grams in every mole.

01:36 I put the grams in the denominator because i want grams to cancel.

01:41 So grams will cancel, and now we have moles in our numerator.

01:45 Next, let's work on converting our denominator from milliliters to liters.

01:50 We know there are 1 ,000 milliliters in one liter.

01:55 So this time i put milliliters in the numerator because i want that to cancel...

Question

In the laboratory you dissolve 21.9 g of ammonium chloride in a volumetric flask and add water to a total volume of 125 mL. What is the molarity of the solution? What is the concentration of the ammonium cation? What is the concentration of the chloride anion?

Please give Ace some feedback