Chemistry with Mr. Faucher Preparing Molar Solutions Name__________________________ To prepare a 1.0-Molar solution of sucrose sugar in a 1-Liter volumetric flask, the mass of 1 mole of sugar (solute) needs to be weighed out and put into the 1-L flask. Then water (solvent) is added to the 1-L mark, making a 1-L volume of solution. To prepare a molar solution of a certain concentration, just use the following 3-step process: moles (Size of flask used) X (Molar concentration desired, in 1 L ) X (molar mass of solute) This 3-step process is demonstrated below for the 1.0-M sucrose solution discussed above: 1.0 L 1.0 mole C12H22O11 342.0 g C12H22O11 x x = 342.0 g C H O 1.0 L 1 mole C12H22O11 12 22 11 size of flask molar concentration molar mass amount to be added to flask Even the more-complicated preparations of other molar solution concentrations follow this 3-step process. How many grams of potassium phosphate, K3PO4, would you add to a 250-mL volumetric flask to make a 0.200-M solution? (Hint: 0.200 M means the concentration is 0.200 moles of K3PO4 per 1,000 mL of solution. Remember, 1 L = 1,000 mL.) 250 mL 0.200 mole K3PO4 212.3 g K3PO4 x x = 10.6 g K PO 1,000 mL 1 mole K3PO4 3 4 size of flask molar concentration molar mass amount to be added to flask ANSWER: An amount of 10.6 g K3PO4 is weighed out and put into the small 250-mL volumetric flask. Then water is added until the solution reaches the 250-mL mark. Chemistry with Mr. Faucher Preparing Molar Solutions Name__________________________ 1. A lab experiment for a class of students requires 250 mL of 0.15 M NaOH. How many grams of the white sodium hydroxide pellets should be put into a 250-mL volumetric flask? How much volume will the NaOH solution take up in the flask when you are done? 2. Another lab experiment requires 500 mL of a 0.20-M solution of silver nitrate, AgNO3. How many grams should you weigh out and put into the 500 mL volumetric flask before adding water to the 500-mL mark? 3. A liter of a 1.0-M solution of copper II sulfate is needed for a lab. How many grams of CuSO4 should you add to the 1-L volumetric flask before adding water to the 1-L mark? 4. What is the definition of molarity? Chemistry with Mr. Faucher Advanced (*) Molarity Problems Name____________________ 1. An amount of 2.47 moles of HNO3 is dissolved to make a 75.0-mL aqueous solution of hydrochloric acid. What is the molarity (molar concentration) of the resulting solution? 2. An amount of 8.38 g of KNO3 is dissolved in enough water to make 0.290 liters of solution. What is the resulting molarity (concentration) of this potassium nitrate solution? *3. How many moles of K2CrO4 are contained in 125 mL of a 3.88-M concentration of the potassium chromate solution? *4. How many moles of glucose are contained in a 2.33L solution of 0.480 M C6H12O6? *5. An experiment calls for 0.500 mole sodium hydroxide. How many mL of a 3.00 M NaOH solution are required? *6. How many grams of copper II nitrate are contained in 345 mL of 0.380 M Ca(NO3)2? 7. How many grams of sodium hydroxide do you need to put into a 250-mL volumetric flask to achieve an aqueous solution concentration of 0.500 M NaOH? .