Properties and counting particles in solutions

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Solutions: Crash Course Chemistry #27


1. Identify the solute and solvent in each solution.

(a) 80-proof vodka (40% ethyl alcohol)

(b) oxygenated water

(c) antifreeze (ethylene glycol and water)

2. What are the dissolved particles in a solution containing a molecular solute? What is the name for this kind of solution.

3. A KNO3 solution containing 110 g KNO3 per 100 g of water is cooled from 60 °C to 0 °C. What happens during cooling? Does all of the solute stay dissolved? If not, how much is not dissolved?

Concentrated vs dilute vs strong vs weak

Strong and weak electrolytes differ in the degree of ionization but concentrated and dilute solutions differ in the amount of solute dissolved. So strong electrolytes like HCl are always strong even in dilute solutions. By contrast, weak electrolytes are always weak even when you have a fairly concentrated solution (like 10M).

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Concentration-counting particles


4. A soft drink contains 32 mg of sodium in 309 g of H2O. What is the concentration of sodium in the soft drink in mass percent?

5. Calculate the molarity of each solution.

(a) 1.54 mol LiCl in 22.2 L of solution

(b) 0.101 mol of LiNO3 in 3000 mL of solution

(c) 0.30 g of glucose (C6H12O6) in 76.2 mL of solution

6. How many grams of solute are present in 355 mL of 0.210 M KNO3?

7. Calculate the volume needed to make the following solutions.

(a) 0.40 M Mg(NO3)2 solution containing 96 g of Mg(NO3)2?

(b) What volume (L) of 0.750 M KCl solution contains 25.0 g of KCl?

Solution dilution

You have already done this but this is a technique and a handy formula for diluting a more concentrated solution to make a more dilute solution.

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1. We can think of stoichiometry also when it comes to just dissolving solutes. Back to a question from the previous day: How many particles are generated when the following dissolve? KNO3, MgCl2, NaC2H3O2 What is the concentration of each ion if 0.1M of the solute dissolves?

2. Describe how you would make 500.0 mL of a 0.200 M NaOH solution from a 15.0 M stock NaOH solution.

3. How much of a 5.0 M sucrose solution should you use to make 85.0 mL of a 0.040 M solution?

4. Mg(OH)2 is a strong electrolyte. Determine the concentration of each of the individual ions in a 0.700 M Mg(OH)2 solution.

[Mg2+] = [OH-] =

5. Determine the concentration of Cl- in each aqueous solution. (Assume complete dissociation of each compound.) (a) 0.20 M NaCl

(b) 0.2 M CuCl2 (c) 0.2 M AlCl3

What can you do to help your understanding?

Chemistry is a subject that must be practiced everyday if possible. Work through the lecture examples stopping the video clips and then restarting to check yourself. Take advantage of the practice in Mastering Chemistry to give you the practice you need to be successful. DO NOT PROCRASTINATE! Check announcements on Sakai (USA) everyday. Keep a printed copy of the most recent course calendar (included in syllabus) next to your work area. Email me with questions!!