[alt-photo] Re: Zia standard solutions

[Terry King]

 I thought that it might be helpful if I were to compare instructions on how to prepare a percentage solution with how to prepare a molar solution.


Terry


1. Percentage solution.


Take one gramme of salt, sodium chloride, add water to 100 ml.


2. Molar solution.












Molar solutions are the most useful in chemical reaction calculations because they directly relate the moles of solute to the volume of solution.
Formula
The formula for molarity (M) is: moles of solute / 1 liter of solution or gram-molecular masses of solute / 1 liter of solution.
Examples

The molecular weight of a sodium chloride molecule (NaCl) is 58.44, so one gram-molecular mass (=1 mole) is 58.44 g. We know this by looking at the periodic table. The atomic mass (or weight) of Na is 22.99, the atomic mass of Cl is 35.45, so 22.99 + 35.45 = 58.44.
If you dissolve 58.44g of NaCl in a final volume of 1 liter, you have made a 1M NaClsolution, a 1 molar solution.

Procedure

To make molar NaCl solutions of other concentrations dilute the mass of salt to 1000ml of solution as follows:
0.1M NaCl solution requires 0.1 x 58.44 g of NaCl = 5.844g
0.5M NaCl solution requires 0.5 x 58.44 g of NaCl = 29.22g
2M NaCl solution requires 2.0 x 58.44 g of NaCl = 116.88g