Seawater is approximately 4.0% by mass dissolved ions, 85% of which are from NaCl. (a) Find the

Seawater is approximately 4.0% by mass dissolved ions, 85%...

Key Concepts

Mass Percent Composition

This concept involves expressing the mass of a particular component (such as a solute) as a percentage of the total mass of the mixture. It is calculated by dividing the mass of the component by the total mass of the mixture and then multiplying by 100. This approach is fundamental for analyzing solutions and mixtures where the concentration of each component is expressed in percent by mass.

Ionic Compound Dissociation

Ionic compounds, like sodium chloride, dissociate into their constituent ions when dissolved in a solvent. Understanding this process is crucial because the mass percentage of the compound in solution must be related to the mass percentages of the individual ions. The dissociation implies that even though the compound is non-ionic as a whole, its ions contribute separately to the total dissolved ion content in the solution.

Molar Mass and Stoichiometry

The molar mass of each element in a compound plays an essential role in determining the mass percentages of each constituent. When calculating the mass percentages of the individual ions produced from the dissociation of an ionic compound, one must account for the atomic masses as well as the stoichiometry, the fixed ratio in which atoms combine. This allows for the conversion of the mass percent of the compound into the mass percents of the individual ions.

Transcript

00:01 So we are given the sea water, the 4 % by mass of sea water is ions, and also within those iron, 85 % with you sodium chloride.

00:08 So first of all, we would like to find out what would be the mass percentage of saline chloride in overall seawater.

00:16 And also what we've did, the mass percentage of individual sodium iron and chloride iron in sea water.

00:22 Okay, so in order to solve the first one, we know that the overall mass, 4 % of that will be ions.

00:32 And within that 4%, 85 % of that will be sodium chloride.

00:37 So the vast percentage of sodium chloride, we have our 4 % of total iron, multiply with 85 % of the sodium chloride, and then we will have the overall percentage.

00:49 So we have 0 .04 times 0 .85, or you can say that it's 4 % times 85%, and then we should be able to find that is 3 % 4 % by mass of the sea water will be corresponding to sodium chloride.

01:07 So what will be the massive percentage of sodium and chloride in water? so from our previous part, we can find that the overall 3 .4 % will be contributed by sodium chloride.

01:24 Okay, so when we actually look at sodium chloride, containing one sodium and one chloride in the formula.

01:29 So from here, we can file the mass percentage of sodium and chloride in the formula.

01:39 Okay, so let's file the total molar mass.

01:43 Total molar mass, we have our sodium plus chloride.

01:51 So roughly around 58.

01:53 It would be a little different depends on what moon mass is used, but it will roughly around 58 gram per mole.

02:00 Okay, so for the number of, i mean for the motor mass of sodium, for the mass percentage from this formula, from this formula, we can take our motor mass of our sodium divided by the overall weight...

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