How many grams of Na2SO4 (142.04 g · mol?¹) are needed to...

How many grams of Na2SO4 (142.04 g · mol?¹) are needed to prepare 125.0 mL of 2.50 mM solution of Na? (2 points)? What’s the concentration in ppm of Na? in this prepared solution? 22.2 mg Na2SO4 and 57.5 ppm 11.1 mg Na2SO4 and 57.5 ppm 44.4 mg Na2SO4 and 115 ppm 22.2 mg Na2SO4 and 115 ppm 44.4 mg Na2SO4 and 57.5 ppm

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00:01 Hi, so we are calculating for the mass of sodium sulfate based on the given information here.

00:08 So we have the concentration of sodium ion in the solution.

00:15 So first we will solve for the number of moles of sodium.

00:22 If we have 2 .50, this is millimolar.

00:26 Let's convert this to molar.

00:30 1000 millimolar is equivalent to 1 molar and 1 molar is equivalent to 1 mole per liter of the solution.

00:41 And then we'll just multiply the volume, that's 125 ml and convert them all to liters.

00:47 1000 ml is 1 liter.

00:50 Now let's cancel some units, millimolar, molar, ml, and then liters.

00:56 And as you can see, the remaining unit is moles since we're solving for n.

01:00 So the number of moles of sodium ion is 3 .125 times 10 to the negative 4, this is moles of sodium.

01:09 And then solving for the mass of na2so4 using the number of moles of sodium, we have 3 .125 times 10 to the negative 4, this is moles of sodium.

01:22 For every 1 mole of sodium sulfate, we have 2 moles of sodium.

01:31 This is just stoichiometry.

01:33 And then we'll multiply the molar mass of na2so4, that's 140 to 0 .04 grams per mole.

01:43 And then we'll cancel some units, moles of sodium, moles of na2so4, and we'll get 0 .0222, this is grams of na2so4...

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