A solution contains 7.5% by mass NaCl and 2.5% by mass KBr. What mass of each solute is containe

A solution contains 7.5% by mass NaCl and 2.5% by mass KBr....

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Key Concepts

Proportional Reasoning

Proportional reasoning involves using the known percentage composition to set up a relationship between the total mass of the solution and the mass of the solute. By applying the percentage as a fraction of the total mass, one can compute the exact mass of each solute in the solution. This approach is a fundamental calculation technique used in various chemical and quantitative problems.

Solute Mass Calculation

Calculating the mass of a solute in a solution involves multiplying the total mass of the solution by the mass percent (expressed as a decimal) of the solute. This method is a straightforward application of the concept of percentage and is essential for determining the specific amounts of various components within a mixture.

Mass Percent Composition

Mass percent composition refers to the ratio of the mass of a solute to the total mass of the solution, expressed as a percentage. It is a common way to describe the concentration of a substance within a mixture by indicating what portion of the total mass is due to the solute. This concept is crucial when determining the actual mass of a solute present in a solution from its percentage concentration.

Transcript

00:01 The question is asking us to bind the mass of each solute contained in 125 grams of solution.

00:11 So our two solutes are nacl or sodium chloride and kbr, which is potassium bromide.

00:20 So we are given the percent by mass of each of these solutes and we are also given mass solution.

00:28 So i have written out the equation for percent by mass, and that is equal to the mass of the solute, which is what we were trying to find, divided by the mass of the solution times 100.

00:41 So first, we're going to start with the sodium chloride and find the mass of sodium chloride.

00:48 So we are given 7 .5%, and i'm just going to write in everything we are given into the equation.

00:55 So we are given 7 .5 % by mass of nacl.

01:00 And that is equal to the mass of nacl, which is our solute, which we don't know you're solving for that.

01:07 So i'm just going to write x as our unknown.

01:10 And that is divided by the mass of the solution, which we are given to be 125 grams.

01:18 And that is multiplied by 100.

01:24 So first step is to divide both sides by 100.

01:28 So that we can isolate 4x.

01:33 And what that will do is that we'll cancel out this term.

01:39 And we'll give us this 7 .5 divided by 100 will give us 0 .075...

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