University:
University of Arizona
Course:
CHEM 141 | General Chemistry Lecture I
Academic year:

2017
Views:

249

Pages:

2
Author:

CloudMaster

This problem requires us to calculate the molarity of a solution. The given data includes the amount of solute and the volume. The problem states: "Calculate the molarity of a solution made by dissolving 23.4 grams of sodium sulfate." So, sodium sulfate is the solid in question. Enough water to form 125 milliliters of solution. This is the volume that we are going to prepare of this solution. So, we are given the number of grams of the solid and the volume of the solution and need to calculate the molarity. As you know, molarity is equal to moles of the solid divided by the volume in liters of the solution. And basically, what we need to do is convert the number of grams of sodium sulfate to moles. That would be the mass of the solid. Then, we need to change the unit of milliliters to later adjust the volume. We would need to change that unit so we can have moles over liters in the equation of sodium sulfate we have. Next, we need to determine the molarity of the solution. To find the molarity, we'll use the formula: Molarity = moles of solute / liters of solution In this case, the moles of sodium sulfate is 100.165 moles, and the volume of the solution is given in milliliters. To convert milliliters to liters, we divide by 1000: Volume (liters) = volume (milliliters) / 1000 So, if we have a volume of 250 milliliters, the volume in liters would be 250/1000 = 0.25 liters. Now we can calculate the molarity: Molarity = 100.165 moles / 0.25 liters Molarity = 400.66 moles/liter Therefore, the molarity of the sodium sulfate solution is 400.66 moles/liter to liters by using the definition of one liter is equal to one thousand milliliters. So, we can cancel out the units of milliliters and we only have the volume in liters. Now, we just substitute in the equation of molarity. It will be 0.165 moles over 0.125 liters, which is equal to 1.32 moles of sodium sulfate divided by liters of. Solution, or one point 32 molar molarity of sodium sulfate. Because the numerator is only slightly larger than the denominator, it is reasonable for the answer to be a little over one molar. The units mol/L are appropriate for molarity, and three significant figures are appropriate for the answer because each of the initial pieces of data are. Here, they have three significant figures, so this is how you can calculate the molarity of a solution given the mass of the solute and the volume of the solution. Remember that with molarity, you can also calculate the moles of solute, which can be converted to grams of solute. Additionally, you can calculate the volume of the solution you need to prepare if you have the molarity. And also, the moles. Okay, so remember that the equation for molarity is used to determine the molarity of a solution. You determine the amount of the solid in the solution or you can also determine the volume of the solution.