From: | "Lee & Peggy Wenk" |

It is the number of replaceable hydrogen atoms. The charge of one hydrogen atom is +1. So multiply the number of replaceable hydrogen atoms by (+1). In hydrochloric acid, the formula is HCl. There is 1 H, so it is 1 x (+1), so the valence is 1. In sulfuric acid, the formula is H2SO4. (Sorry, can't make my email do subnumbers.). There are 2 replaceable H, so it is 2 x (+1), so the valence is 2. It gets confusing if you are trying to make a normal solution, and the chemical does not have replaceable hydrogen atoms, but does have a positively charged atom. Or if you have a polyatom (atoms that always stay together, like hydroxide (OH) or phosphate (PO4) or carbonate (CO3) or sulfate (SO4)). If the hydrogen is in the polyatom is NOT counted as a replaceable atom. So you have to count the number of positive charges of the non-polyatom. Aluminum hydroxide is Al(OH)3. There is one aluminum atom, with a +3 charge. There are 3 hydroxide (OH), with a charge of -1 each. The hydrogen in the hydroxide is not replaceable. It is "stuck" in the hydroxide. You have to look at the "replaceable" positive charges. So there is 1 Al with a +3 charge, so that is 1 x (+3) = valence of 3. You need to know the charge of the positive atom (from the periodic table or other chemical table) and multiply it by the number of positive atoms in that compound. CaO is 1 calcium x (+2) = 2 valence. K2CO3 is 2 potassium atoms x (+1) = 2 valence. To make this even worse, if you are making a normal solution by diluting a liquid (solute such as HCl or H2SO4) into the water (solvent), the formula becomes even more complicated, as you have to include the concentration (c) of the solute as well as the specific gravity (sp). Both of these figures are usually obtained off the label of the bottle or from the MSDS. (Water has a specific gravity of 1. If the solution is heavier/thicker than water, the sp will be slightly larger than 1.0. If the solution is lighter/runnier than water, the sp will be less than 1.0.) And HCl and H2SO4, for example, are not pure acid. HCl is about a 33-37% solution when it is concentrate, with a specific gravity of about 1.1. If anyone wants the formula of normality for liquids, I'll post that tonight. I have it at work, and don't remember off the top of my head, and have to leave early for work because of the 7 inches of snow that hit us last night. Peggy A. Wenk, HTL(ASCP)SLS William Beaumont Hospital Royal Oak, MI 48073 ----- Original Message ----- From:To: Sent: Wednesday, January 14, 2004 2:53 PM Subject: [Histonet] normal solutions question > Thank You guys for all the responses i have received...but im still STUCK i > don't understand how to come up with the positive valence, or number of > dissociable or replaceable hydrogen ions.....this is the number that i divide the > molar weight with to get the normal weight....every problem i have worked out i > seem to be dividing by 2 and that doesn't make since to me. > _______________________________________________ > Histonet mailing list > Histonet@lists.utsouthwestern.edu > http://lists.utsouthwestern.edu/mailman/listinfo/histonet > _______________________________________________ Histonet mailing list Histonet@lists.utsouthwestern.edu http://lists.utsouthwestern.edu/mailman/listinfo/histonet