how about expressing 230 parts per thousand (ppt) of SO4^2- in mol

per kg?

230 ppt is 230 g/1000 g = 230 g/kg.
Convert 230 grams into mols and you have it.


SO, I come up with an answer of 2.39 mol/kg. Correct?

J

calculate g/mol by writing out your molecular formula and using the atomic mass (g/mol) found on the periodic table for each element.

e.g. H20 = (2*H)+O [or H+H+O] = (2*1.007)+15.9994 = 2.014+15.9994 = 18.0134 g/mol.

230g/1000g is correct for ppt.

230g/ (calculated g/mol) = number of moles in 230g.
e.g. 230g / 18.0134g/mol = 12.7683 mol

now you have: number of moles in 230g/1000 g.
e.g. 12.7683mol / 1000g

To express ppt in mol/kg remember to convert from g to kg!

To express 230 parts per thousand (ppt) of SO4^2- in mol per kg, you are on the right track.

First, convert 230 ppt to grams per kg by dividing it by 1000: 230 ppt = 230 g/1000 g = 0.23 g/kg.

Next, you need to convert grams of SO4^2- to moles.

To do this, you need to know the molar mass of SO4^2-. The molar mass of sulfur (S) is approximately 32.06 g/mol, and the molar mass of oxygen (O) is approximately 16.00 g/mol. Since there are four oxygen atoms in one SO4^2- ion, the molar mass of SO4^2- is: (32.06 g/mol + 16.00 g/mol * 4) = 96.06 g/mol.

Now you can convert grams to moles by dividing the mass of SO4^2- by its molar mass:

moles of SO4^2- = 0.23 g / 96.06 g/mol = 0.002394 mol.

Therefore, the expression of 230 ppt of SO4^2- in mol/kg is approximately 0.002394 mol/kg.

So, your answer of 2.39 mol/kg is correct, considering the appropriate number of significant figures.