Molarity and Dilutions Concentration of Solutions Molarity and

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Molarity and Dilutions Concentration of Solutions

Molarity and Dilutions Concentration of Solutions

Molarity and Dilutions E. Q. : How is the concentration of a solution calculated

Molarity and Dilutions E. Q. : How is the concentration of a solution calculated (molarity)?

Molarity – Measurement of the concentration of a solution (how much solute is in

Molarity – Measurement of the concentration of a solution (how much solute is in a volume of solution) Molarity (M) is equal to the number of moles of solute (n) per liter of solution Molarity (M) = moles of solute / liters of solution Units: M = mol / L

Molarity Be careful not to get molarity and moles mixed up. Moles measures the

Molarity Be careful not to get molarity and moles mixed up. Moles measures the amount of material you have. Molarity measures the concentration of the material.

Molarity Suppose we had 1. oo mole of sucrose and proceeded to mix it

Molarity Suppose we had 1. oo mole of sucrose and proceeded to mix it into some water. It would dissolve and make sugar water. We keep adding water, dissolving and stirring until all the solid was gone. We then made sure that when everything was well-mixed, there was exactly 1. 00 liter of solution. What would be the molarity of the solution? M = 1. 00 mole / 1. 00 liter = 1. 00 mol/L or 1. 00 M Often, instead of writing the units as mol/L, a capital M is used (M = mol/L)

Molarity Examples 1. Calculate the molarity of a solution prepared by mixing 1. 5

Molarity Examples 1. Calculate the molarity of a solution prepared by mixing 1. 5 g of Na. Cl in 500. 0 m. L of water First calculate the moles of solute in the solution: 1. 5 grams Na. Cl 1 mol Na. Cl = 0. 026 mol Na. Cl 58. 443 grams Na. Cl Next convert m. L to L: 0. 500 L Last, plug the appropriate values into the correct variables in the equation: M = n / V = 0. 026 mol / 0. 500 L = 0. 052 mol/L or 0. 052 M

Molarity Examples 2. Calculate the mass of Na. OH needed to prepare 1. 00

Molarity Examples 2. Calculate the mass of Na. OH needed to prepare 1. 00 L of a 1. 50 M solution. To do this, the formula for molarity needs to be rearranged in order to solve for the number of moles: M = moles / liters moles = M x liters Numbers are then plugged into rearranged formula: moles = (1. 50 mol/L) x (1. 00 L) = 1. 50 mol Na. OH We then find the grams in the 1. 50 mol of Na. OH by using dimensional analysis 1. 50 mol Na. OH 39. 997 grams Na. OH 1 mol Na. OH = 59. 9955 grams Na. OH = 60. 0 grams Na. OH

Molarity Examples 3. 965 grams of Na. OH is used in preparing a 1.

Molarity Examples 3. 965 grams of Na. OH is used in preparing a 1. 5 M solution. What volume of solution can be made? First calculate the moles of solute in the solution: 965 grams Na. OH 1 mol Na. OH = 24. 1 mol Na. OH 39. 997 grams Na. OH We now rearrange the formula for molarity to solve for volume (liters): M = moles / volume = moles / M Numbers are then plugged into rearranged formula: volume = (24. 1 mol) / (1. 5 mol/L) = 16. 0666 L = 16 L

Your Turn…… 1. Sea water contains roughly 28. 0 g of Na. Cl per

Your Turn…… 1. Sea water contains roughly 28. 0 g of Na. Cl per liter. What is the molarity of sodium chloride in sea water? 2. What is the molarity of 245. 0 g of H 2 SO 4 dissolved in 1. 00 L of solution? 3. How many moles of Na 2 CO 3 are there in 10. 0 L of 2. 0 M solution? 4. What weight (in grams) of H 2 SO 4 would be needed to make 750. 0 m. L of 2. 00 M solution? 5. What volume of 18. 0 M H 2 SO 4 is needed to contain 2. 45 g H 2 SO 4?

Dilutions Dilution: The process of decreasing the concentration of a stock solution by adding

Dilutions Dilution: The process of decreasing the concentration of a stock solution by adding more solvent to the solution. - The solvent added is usually the universal solvent, known as water. The more solvent you add, the more diluted the solution will get. - A stock solution is a concentrated solution that will be diluted to a lower concentration for actual use

Dilutions The equation for dilution is M 1 V 1=M 2 V 2 stock

Dilutions The equation for dilution is M 1 V 1=M 2 V 2 stock solution= diluted solution • M 1= molarity of the stock solution • M 2= molarity of the diluted solution • V 1= volume of stock solution • V 2= volume of diluted solution Basically, dilution calculations involve figuring out the final concentration or volume ( depending on what’s given and what’s known) after a volume or concentration has been changed. In dilution equations, you are given three things and you need to find the fourth component.

Dilution Examples 1. If I add 25 m. L of water to 125 m.

Dilution Examples 1. If I add 25 m. L of water to 125 m. L of a 0. 150 M Na. OH solution, what will the molarity of the diluted solution be? 2. If I add water to 100. m. L of a 0. 150 M Na. OH solution until the final volume is 150. m. L, what will the molarity of the diluted solution be?

Dilution Examples 3. I have 345 m. L of a 1. 5 M Na.

Dilution Examples 3. I have 345 m. L of a 1. 5 M Na. Cl solution. If I boil the water until the volume of the solution is 250 m. L, what will the molarity of the solution be? 4. How much 0. 05 M HCl solution can be made by diluting 250 m. L of 10 M HCl?