Determining the mass of solute to create a desired solution 20 points Name:__________________________________ Period:______________ The molarity of a solution is the number of moles of a substance dissolved in 1 liter of water. You often need to determine the mass of a solute to create a solution of a desired molarity. This is done as follows: 1. Determine the average atomic mass if the sample is an element, or the gram formula weight if it is a compound. 2. Multiply the desired molarity by the grams/mole computed in step 1. Examples: How many grams of NaCl are needed to create 1 L of a 2 molar solution? NaCl has a gram formula weight of 58. 2 How many grams of NaCl are needed to create 1 L of a .1 molar solution? .1 Sometimes you want to make less than a liter of a solution. How many grams of NaCl are needed to create 500 mL of a .1 molar solution? .1 Compute the number of grams of the compound is needed to create the solution in each of the following samples. Round to 2 places to the right of the decimal. Attach solutions and show all work, as above. (2 points each) Show all work.
How many grams of KNO3 are needed to create 1L of a .2 molar solution? (5 points) How many grams of KNO3 are needed to create 250 mL of a .2 molar solution? (5 points) |
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