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The terms "concentrated" and "dilute" provide qualitative methods of describing concentration.Although qualitative observations are necessary and have their place in every part of science, including chemistry, we have seen throughout our study of science that there is a definite need for quantitative measurements in science. In this section, we will explore some quantitative methods of expressing solution concentration.
If we said the mixture was \(10\%\) acetic acid, this would be more concentrated than the vinegar solution.
The solution on the left is more concentrated than the solution on the right because there is a greater ratio of solute (red balls) to solvent (blue balls) particles. The solution on the right is more dilute (less concentrated).
SOLUTION We can substitute the quantities given in the equation for mass/mass percent: \(\mathrm\) Sometimes you may want to make up a particular mass of solution of a given percent by mass and need to calculate what mass of the solute to use.
Using mass percent as a conversion can be useful in this type of problem.
The mass of the solution is mass of solution = 25.0g sugar 100.0g water = 125.0 g The percent by mass would be calculated by: \[\text = \frac \times 100\% = 20.0\% \: \text\] Example \(\Page Index\) A saline solution with a mass of 355 g has 36.5 g of Na Cl dissolved in it.
What is the mass/mass percent concentration of the solution?
Notice that it was necessary to subtract the mass of the \(\ce\) \(\left( 150 \: \text \right)\) from the mass of solution \(\left( 3000 \: \text \right)\) to calculate the mass of the water that would need to be added.
Another way of expressing concentration is to give the number of moles of solute per unit volume of solution.
The dilution equation is used in these circumstances as well.
In a hospital emergency room, a physician orders an intravenous (IV) delivery of 100 m L of 0.5% KCl for a patient suffering from hypokalemia (low potassium levels).