Question

The seven most abundant ions in seawater make up more than 99% by mass of the dissolved compounds. Here are their abundances in units of mg ion/kg seawater: chloride 18,980; sodium 10,560; sulfate 2650; magnesium 1270; calcium 400; potassium 380; hydrogen carbonate 140. (a) What is the mass 96 of each ion in seawater? (b) What percent of the total mass of ions is sodium ion? (c) How does the total mass % of alkaline earth metal ions compare with the total mass 96 of alkali metal ions? (d) Which make up the larger mass fraction of dissolved components, anions or cations?

Answer 1

Here's what I get

Step-by-step explanation:

(a) Mass % of each ion

`\text{Mass \%} = \frac{\text{mass}}{\text{total mass}} * 100 \, \%\\\\= \frac{\text{mass}}{34 380} * 100 \, \%\\= 2.903 * 10^(-3) *\text{`

I used this template to calculate the percentages in the table below.

Ion Abundance Mass %

Na⁺ 10 560 30.72

K⁺ 380 1.11

Alkali metals 10 940 31.82

Mg²⁺ 1 270 3.69

Ca²⁺ 400 1.16

Alkaline earth metals 1 670 4.86

Total metal ions 12 610 36.68

Cl⁻ 18 980 55.20

SO₄²⁻ 2 650 7.71

HCO₃⁻ 140 0.41

Anions 21 770 63.32

TOTAL 34 380 100.00

(b) 30.72 % of the total mass is sodium ion.

(c) Alkaline earth metals vs alkali metals

`\frac{\text{alkaline earth}}{\text{alkali}} = (4.86)/(31.82) = (1 )/(6.55)`

The mass percent of alkali metal ions is 6.55 times that of alkaline earth metal ions.

(d) The mass of anions is greater than that of cations.