<span>When one talks about ppm in a liquid solution someone means mg/L so we would not be using the density. This usually means ug/g or mg/kg
0.115 g Na^+ * 10^6 ug/1 g = 115000 ug/g
4.55 L * 1000 mL/1L = 4550 mL
Concentration of Na^+ in ppm:
115000 ug/g /4550 mL = 25.27 pm of sodium ion</span>
<span>With any element, there are a range of isotopes . . . a weighted average mass is used because there exist different isotopes of that element, each of varying mass. A weighted average accounts for the fact that the average mass (that may likely be measured from a random sample of the element) will most likely reflect the average mass of the more abundant isotopes. So the weighted average mass will be most comparable to the more abundant isotopes.</span>
(3) both a chemical and a physical change can reach equilibrium. For example, an acid-base reaction can achieve equilibrium (chemical change), and a system can achieve dynamic equilibrium (phase changes from liquid to gas, for example), which is a physical change.
<span> They have stronger forces of attraction between each other.</span>
