1 / 32

Concentration

Concentration. EQ. What is concentration?. Describe ways that concentration can be expressed and calculated. You made 2 saturated solutions, NaCl and MgSO 4. Which saturated solution had more solute dissolved in it? MgSO 4 How much MgSO 4 was needed to saturate 30 mL of water?

kalli
Download Presentation

Concentration

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Concentration

  2. EQ. What is concentration? • Describe ways that concentration can be expressed and calculated

  3. You made 2 saturated solutions, NaCl and MgSO4. • Which saturated solution had more solute dissolved in it? • MgSO4 • How much MgSO4 was needed to saturate 30 mL of water? • On average 28-30 grams or 4 times the amount of NaCl

  4. Stock Solutions • I have 2 MgSO4 solutions. They are not saturated. • Solution 1 is made with 200 mL of H2O and 20g of MgSO4 • Solution 2 is made with the same amount of H2O 200 mL, and 50g of MgSO4

  5. How are these two solutions different? • Both are made with the same substances and the same amount of solvent, 200 mL of H2O. • They differ in the amount of solute, MgSO4, dissolved in the H2O.

  6. Concentration • When two solutions are made with the same amount of solvent (H2O), but different amount of solute (MgSO4), the solutions differ in concentrations. • The solution with more solute is more concentrated.

  7. Concentration • :a ratio between the amount of solute and the amount of solvent in a solution. • The more solute there is dissolved in a volume of solvent, the more concentrated the solution. • Is solution 1 or solution 2 more concentrated? • Solution 2

  8. Solution 2 is more concentrated • Solution 2 is made with 50g of magnesium sulfate in 200 mL of water • Solution 1 is made with 20g of magnesium sulfate in 200 mL of water. • 50g > 20g • Solution 2 has more solute dissolved in the same amount of solvent than solution 1

  9. Find the mass of the samples • If I find the mass of 40 mL samples of these two solutions, what do you think I will discover? • Will the masses of the two equal volumes be equal or will the mass of one 40 mL sample be greater than the other?

  10. Volunteers to help • 2 students • Find mass of 40 mL samples. • Solution 1 20g/200 mL is about 40.5g • Solution 2 50g/200 mL is about 42.5g

  11. We find that…. • The more concentrated solution has the greater mass than the less concentrated solution

  12. What is the relationship between concentration of solutions and their masses? • When you find the mass of equal volumes of solutions made with the same substances, the sample with the greatest mass is most concentrated. • Conversely, the sample with the lowest mass is the least concentrated. • There is a direct relationship between mass and concentration.

  13. Remember… • Mass can be used to determine which of several solutions is most concentrated onlywhen equal volumes of solutions made with the same substances are compared.

  14. MgSO4 Solutions • Today each group will make their own solution with MgSO4 and H2O. • After the solutions are made, we will investigate them to see if we can figure out which solution is most concentrated. • Watch as I do the first one that is 5g MgSO4 and 25g H2O • Your recipe is…..(circle it/star it)

  15. RecipesTable MgSO4 H2O • Table 1 5g 25g • Table 2 8g 20g • Table 3 12g 20g • Table 4 8g 40g • Table 5 10g 25g • Table 6 15g 25g • Table 7 10g 50g • Table 8 16g 40g

  16. Materials • Each tray • MgSO4 station • Mass stations (2) • Water from sink • *safety rules

  17. Make Solutions • Measure the water accurately. Use pipette to get the volume exact. • Measure the mass of MgSO4 accurately. Zero the balance with the cup on the pan. • Wear protective eyewear. Mix and stir carefully. Avoid spills. • NO SQUIRTING! NO SPLASHING!

  18. Compare Magnesium Sulfate Solutions • Which of the solutions we made is most concentrated? • How can we find out? • Make a plan.

  19. Plan • Do you agree… on a volume of solution that every group will measure and find the mass. • *The volume should not exceed 20 mL • Measure and record the mass of the 20 mL samples • Compare the masses of the 20 mL samples

  20. Record the results • On member from each table report results. • Add to chart on overhead transparency 27

  21. Discuss • Transcribe into MgSO4 solutions sheet • Answer question 1 • General rule: • Mass per volume • Which are most concentrated? • Recipes from table 2 (12 g of MgSO4 and 20 g of H2O) and from table 5 (15 g MgSO4 and 25 g of H2O)

  22. Calculate Mass Per Unit Volume • The concentration of solutions is most easily compared when the concentration is expressed as mass per unit volume, that is, the mass (number of grams) of 1mL. • Calculate the concentration of the solutions in grams per milliliter: g/mL = mass of 20mL (g) 20 mL

  23. Summary 1 • A Solution is: a mixture of two or more substances. • In a solution one substance, the solute, is dissolved in the other substance, the solvent. • When a solute dissolves, it is broken into particles by solvent particles. • The solute particles are carried into the solvent by solvent particles. • Solute particles are distributed uniformly throughout the particles of the solvent.

  24. Summary 2 • There is a limit to the amount of solute that can dissolve in a given amount of solvent. • When the solvent has no more room for solute particles, the solution is saturated. • Additional solute will remain undissolved on the bottom of the container.

  25. Summary 3 • The amount of solute dissolved in a volume of solvent determines the concentration of the solution. • Concentration is: a ration of solute to solvent in a solution. • The substances in a solution are not changed chemically when they dissolve. • Often evaporation will separate the solvent and the solute.

  26. Reading • Concentration- Resource book articles • Complete Lab Manual page 85

  27. Mid-Summative Exam 8 • Friday

More Related