determine the amounts of solute and solvent needed to prepare the following solutions.
2.0 M aqueous NaCl solution
1.0 m aqueous KCl solution
25% by mass aqueous MgCl2 solution
1 is M = moles/L
2 is moles/kg solvent
3 is 25 g/100 g soln.
To determine the amounts of solute and solvent needed to prepare the given solutions, we need to know the desired volume of the solution. Once we have that information, we can use the formulas for molarity and mass percent to calculate the amounts of solute and solvent.
Let's break down each solution:
1. 2.0 M aqueous NaCl solution:
To prepare a 2.0 M solution, we need to know the desired volume, let's say it's V liters. Molarity (M) is defined as moles of solute per liter of solution, so we need to dissolve enough NaCl in V liters of water to have a concentration of 2.0 M.
To calculate the amount of solute needed, we use the formula:
moles of solute = molarity (M) × volume (L)
In this case, we want 2.0 moles of NaCl per liter, so for V liters, we need:
moles of NaCl = 2.0 M × V L
2. 1.0 M aqueous KCl solution:
Similar to the previous solution, here we want a concentration of 1.0 M, so we use the same formula:
moles of solute = molarity (M) × volume (L)
In this case, we want 1.0 moles of KCl per liter, so for V liters, we need:
moles of KCl = 1.0 M × V L
3. 25% by mass aqueous MgCl2 solution:
Mass percent is defined as the mass of solute divided by the mass of the solution, multiplied by 100%. This means that for a 25% by mass solution, we have 25 grams of MgCl2 per 100 grams of solution.
Let's say we want to prepare a solution with a mass of M grams. To calculate the amount of solute needed, we use the formula:
mass of solute = mass percent × mass of solution
In this case, we want 25 grams of MgCl2 per 100 grams of solution, so for M grams of solution, we need:
mass of MgCl2 = (25 / 100) × M grams
To find the amount of solvent, we subtract the mass of solute from the mass of the solution:
mass of solvent = mass of solution - mass of solute
Please note that these calculations assume that the solutes, NaCl, KCl, and MgCl2, are in their anhydrous (water-free) forms. If working with hydrated salts, additional steps to account for the water of hydration may be necessary.