Instruction

1

Suppose 200 or 300 milliliters of water dissolve 58.5 grams of sodium chloride, that is familiar to all of salt. Then, Prilepa water brought the total weight of the solution up to one kilogram. It is easy to guess that the solution in this case will contain 58.5 grams of salt and 941,5 grams of water. What will be the mass fraction of salt?

2

To calculate it is easy, for this amount of salt, divide by the total mass of solution and multiply by 100%, it will look like the following:(58,5/1000) * 100% = 5,85%.

3

Formulate the task a little differently. The same amount of salt dissolved in water, then brought the solution volume up to one liter. What will be the molar concentration of the solution?

4

Remember the definition of molar concentration. This is the number of moles of dissolved

**substance**contained in one liter of solution. What is the mol of salt? Its formula is NaCl, the molar mass is approximately 58.5 per. In other words, in one liter of solution you have contains exactly one mole of salt. You will receive a 1.0 molar solution.5

Now go back to the original conditions of the problem where the total weight of the solution amounted to exactly one kilogram. How do you find the molality of this solution?

6

And here, too, there is nothing difficult. Above you have already figured out that 58.5 grams of common salt have 941, 5 grams of water. Substituting the known values into the formula m = v/M, where M is the value of the molality and v is the number of moles

**of the substance**in the solution, and M is the mass of solvent in kilograms, we get:1,0/0,9415 = 1,062 Moralny solution.Useful advice

The concentration can be expressed in many different ways. For example, using the concepts of "mass fraction", "molarity" (i.e., how many moles of a substance is in 1 liter solution), molality (number of moles of a substance is in 1 kilogram of solvent), etc.