1.)prepare 500mM 100 ML HCL (37% purity, density 1.8)

2.) prepare 0.5N 100 mL HCL(37% purity, density 1.8)

here is a hint: both are the same solutions. But it mattes what stock solution you start from, HCL can never be pure.

To prepare a solution, you need to know the molar concentration or normality required, along with the purity and density of the solute. Let's calculate the steps to prepare both solutions:

1. Prepare 500 mM 100 mL HCL (37% purity, density 1.8):

Step 1: Calculate the molar mass of HCl (Hydrochloric acid):
- H = 1.01 g/mol
- Cl = 35.45 g/mol
Total molar mass = 1.01 + 35.45 = 36.46 g/mol

Step 2: Calculate the volume of concentrated HCl needed:
- The desired final volume is 100 mL.
- The density of the solution is 1.8 g/mL.
- So, the mass of the solution required is 100 mL * 1.8 g/mL = 180 g.

Step 3: Calculate the mass of pure HCl required:
- As the purity is specified as 37%, multiply the mass of the solution by the purity percentage to get the pure HCl mass.
- Mass of pure HCl = 180 g * (37/100) = 66.6 g.

Step 4: Calculate the number of moles of HCl required:
- Moles of HCl = mass of pure HCl / molar mass of HCl.
- Moles of HCl = 66.6 g / 36.46 g/mol = 1.826 mol.

Step 5: Calculate the volume of concentrated HCl needed:
- To prepare a 500 mM (millimolar) solution, multiply the number of moles by the volume in liters.
- Volume of concentrated HCl = moles of HCl * 0.1 L (100 mL = 0.1 L) = 1.826 * 0.1 = 0.183 mL.

So, to prepare a 500 mM 100 mL HCl solution, you need to measure 0.183 mL of concentrated HCl (37% purity, density 1.8) and then dilute it to 100 mL with an appropriate solvent.

2. Prepare 0.5N 100 mL HCL (37% purity, density 1.8):

Step 1: Calculate the molar mass of HCl (Hydrochloric acid) and the molar factor conversion:
- The molar mass of HCl is 36.46 g/mol.
- 1 equivalent (eq) of HCl provides 1 mole of H+ ions.
- N = Normality = Number of equivalents / Volume (in liters).

Step 2: Calculate the number of equivalents of HCl required:
- 0.5N means 0.5 equivalents per liter.
- For 100 mL (0.1 L) of solution, the number of equivalents required is: 0.5N * 0.1 L = 0.05 equivalents of HCl.

Step 3: Calculate the mass of HCl required:
- To find the mass of HCl required, use the molar mass of HCl and the number of moles:
- Mass of HCl = moles of HCl * molar mass of HCl.
- Moles of HCl = equivalents of HCl (0.05 eq) * molar mass of HCl.

Step 4: Calculate the volume of concentrated HCl needed:
- The concentration of the HCl solution is not required as normality is an expression of equivalent concentrations.
- To find the volume of concentrated HCl, divide the mass of HCl required by the density of the solution.
- Volume of concentrated HCl = mass of HCl / density of HCl solution.

Please note that normality calculations require specific equivalents, which can vary depending on the reaction or standard you are following. Ensure you understand the specific requirement for your experiment.