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

Seawater is approximately $4.0 \%$ by mass dissolved ions, $85 \%$ of which are from $\mathrm{NaCl}$. (a) Find the mass $\%$ of $\mathrm{NaCl}$ in seawater.
(b) Find the mass \% of $\mathrm{Na}^{+}$ ions and of $\mathrm{Cl}^{-}$ ions in seawater.

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Key Concepts

Stoichiometry of Ionic Compounds

Stoichiometry of ionic compounds refers to the quantitative relationship between the ions within a compound, dictated by the chemical formula. This concept allows one to calculate the proportionate contribution of each ion to the overall mass of the compound and, consequently, to a solution when the compound is dissolved.

Mass Percent

Mass percent is a way to express concentration by representing the mass of a solute or component as a fraction of the total mass of the mixture, multiplied by 100. It is a fundamental concept in solution chemistry and is widely used to quantify the composition of mixtures.

Ionic Dissociation

Ionic dissociation involves the process by which an ionic compound separates into its individual ions when dissolved in a solvent. This concept is key to understanding the behavior of salts in water, where compounds like sodium chloride split into sodium (Na?) and chloride (Cl?) ions.

Chemical Composition of Solutions

The chemical composition of solutions deals with determining the mass percentages or molar concentrations of the various components in a mixture. This analysis is essential for applications in environmental, analytical, and physical chemistry, ensuring precise knowledge of all constituents.

Transcript

00:01 In this problem, we're going to be working through multiple examples of mass percent.

00:04 We're given that 4 % of all seawater is dissolved ions, and 85 % of that 4 % is nacl, which is table salt.

00:15 So we want the total mass percent of nacl in seawater, and then the total mass percent of the individual ions that make up nacl.

00:23 So first, we're looking for the total mass percent of nacl in seawater, which all we have to do for this is multiply our.

00:31 Two givens.

00:32 We have to convert our percentages into decimals, which is just dividing by, dividing our numbers by 100.

00:37 So 0 .04 times 0 .85.

00:44 And when we multiply that out, we get 0 .034.

00:51 Multiply that by 100 to get 3 .4%.

00:55 So 3 .4 % of all seawater is nacl.

01:01 For the second part, we need to find how much of our sodium ion and our chlorine ion make up what mass percent of each of those is in seawater.

01:12 So to do that, we're going to find the molar mass of nacl.

01:17 Since there's only one atom of each in this molecule, we don't have to multiply anything.

01:22 We just need to find the atomic mass.

01:24 Sodium's is 22 .99.

01:27 Chlorines is 35 .45.

01:30 When we add those together, we get 58 .44.

01:34 Grams per mole...

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