A100. g sample of water contains 0.000 325 g of calcium. what is the concentration of calcium, in ppm? round your answer to 3 significant figures.

Parts per million is a pseudo-unit that denotes a ratio between two units (which could be mass, volume, etc as long as they're consistent). Mass units in mg/kg can be treated as the same as ppm. A 100 g sample of water is the same as 0.1 kg which contains 0.000325 g or 0.325 mg of calcium. Dividing the mass of the solute over the mass of the solvent: 0.325 mg / 0.1 kg gives us 3.25 mg/kg or 3.25 ppm.

the catch is that the top numbers are atomic masses the bottom numbers are the numbers of protons and electrons in an uncharged atom. they are the number of that atoms as you would find them on the periodic table. further, the numbers on the left are used to determine the missing numbers on the right

so here we go

atomic mass

239 + 1 = y + 134 + 3 combine like terms

240 = y + 137             subtract 137 from both terms

240 - 137 = y

103 = y

atomic number

94 = z +54 + 0

94 = z + 54               subtract 54 from both sides.

40 = z

answer