i don't really understand molality. I know that it is a big concept but could someone explain it a little.
the question is how would you prepare a molality solution.
Molarity is about as simple as it gets. The definition is all you need.
The definition of molarity is
Molarity = M = # moles/Liter of solution.
So, to prepare a 1 molar solution, of something, say NaCl, you dissolve 1 mole of NaCl in water, shake it around until all of it dissolved, then make the final volume of the solution to 1 L. Simple, eh what? A 2 molar solution you dissolve 2 moles of NaCl in ......, a 3 M by dissolving 3 moles NaCl.... etc.
What is a mole of NaCl? moles = g/molar mass. So 1 mol of NaCl is about 23 for Na and about 35.5 for Cl or about 58.5 grams for a mole NaCl. (You can look up Na and Cl on the periodic table and get the exact mass if you want it). Since M = mols/L, that can be rearranged to make M x L = moles and L = mols/M.
Please let me know if this doesn't do the job BUT be sure and tell me exactly what is still unclear about it.
thanks i didn't really get molarity either but my question is for molality.
I didn't answer your original question because it makes no sense. There is no such thing as preparing a molarity solution. You can prepare a MOLAR solution or a TWO MOLAR solution but you can't prepare a molarity solution. You CAN add an maount of material to a certain amount of water and ask for the molarity of that solution and it's th same concept. Its mols/L = Molarity. So if you are given 29.25 g NaCl in a final volume of 500 mL (0.50 L), then the solution is M = moles/L. We have 29.25 grams NaCl which is 20.26/58.5 = 0.500 g in 0.500 L = 0.5/0.5 = 1 M.
Molality is a measure of the concentration of a solute in a solution. It is defined as the number of moles of solute per kilogram of solvent.
To understand how to prepare a molality solution, let's assume we want to prepare a 1 molal (1 m) solution of solute A in solvent B. Here's how you can do it:
1. Determine the molar mass of solute A: Find the atomic masses of each element in the formula of solute A, and add them up to get the molar mass.
2. Weigh out the desired mass of solute A: Use a balance to weigh out the mass of solute A required to achieve the desired concentration. For example, if you want 1 mol of solute A, weigh out its molar mass in grams.
3. Measure the mass of the solvent B: Use a balance to measure the mass of solvent B required. Keep in mind that molality is based on the mass of the solvent, not the total solution.
4. Dissolve the solute A in the solvent B: Add the measured mass of solute A to the measured mass of solvent B. Mix them thoroughly to ensure complete dissolution.
5. Calculate the molality: Now that you know the moles of solute A and the mass of solvent B, you can calculate the molality using the formula:
Molality (m) = moles of solute A / mass of solvent B (in kg)
Remember, it's important to convert the mass of solvent B to kilograms by dividing it by 1000, since molality is defined per kilogram of solvent.
Preparing a molality solution requires accurately weighing the masses of both solute and solvent to ensure the desired concentration. It is crucial to handle chemicals and equipment safely and follow appropriate lab procedures.