Objectives: Define solution terms; Calculate solution concentrations & contents; Describe colligative properties
Define the terms: solution, solvent, solute, solubility. Describe a saturated solution, an unsaturated solution, and a supersaturated solution. How do the terms dilute and concentrated relate?
Look in the appropriate chapter of the book and the golossary to make sure you understand the terms used for solutions.
What is an aqueous solution?
the solvent is water
What is the general solubility rule for solvents and solutes?
like dissolves like
What types of solutes do not follow this general solubility rule?
ionic compounds
Which of the following compounds would be soluble in water: KNO3 , AgCl, NaOH, BaCl2 ?
KNO3 , NaOH, BaCl2
Define the Mass-Volume Percent concentration unit.
mass of solute in a solution (in grams) divided by the total volume of solution (in ml), multiplied by 100
What is the molarity of a solution?
moles of solute divided by liters of solution
1.5 grams of solute is dissolved in a 100 ml solution. What would be its concentration in Mass-Volume Percent?
1.5% (m/v)
What would be the molarity if 1 mole of solute was dissolved in 100 ml of solution.
0.1M
A 10M stock solution is used to make a new solution. A 10 ml aliquot of stock is diluted to 100 ml with water. What is the concentration of the new solution?
1.0M
What is a colloid (colloidal dispersion)?
a mixture that contains dispersed particles that are intermediate in size between those of a true solution and those of an ordinary heterogeneous mixture. It contains the dispersed phase and the dispersing medium.
Name the 4 colligative properties.
vapor-pressure lowering, boiling-point elevation, freezing-point depression, osmotic pressure
What is osmosis?
the passage of a solvent thru a semipermeable membrane separating a dilute solution (or pure solvent) from a more concentrated solution.
What is osmotic pressure?
the pressure that must be applied to prevent the net flow of solvent thru the semipermeable membrane due to osmosis
What is the osmolarity of a 1.0M NaCl solution?
2.0 osmo
Define the terms isotonic, hypertonic, and hypotonic. Use them to explain why some solutions will cause red blood cells to lyse (burst apart).
Look up the terms and use them to describe what would happen if red blood cells were put in pure water, 2.0 % NaCl, or 0.9% NaCl (saline).
What is dialysis? What human organ performs this function?
process in which a semipermeable membrane allows the passage of solvent, dissolved ions, and small molecules but blocks the passage of colloidal-sized particles and large molecules. The kidney.
The osmolarity of a 3.0 M NaCl solution is greater than the osmolarity of a 3.0M glucose solution. True or False
True
Red blood cells will shrink in size when placed in an isotonic solution. True or False
False
2.0 liters of a 6.0 M solution would contain 12.0 moles of solute, independent of the identity of the solute. True or False
True
In dialysis, only water or small solute particles pass through the dialyzing membrane True or False
True
For the following substances: A – polar solute, B – polar solvent, C – nonpolar solvent. A is more soluble in C than in B. True or False
False
In a colloidal dispersion solute particles are large enough to be discernible by the naked eye. True or False
False
In a solution, the solvent is always water. True or False
False
Gaseous solutes become more soluble in water with increasing pressure. True or False
True
An increase in temperature will increase the solubility of solids, liquids, and gases in liquids. True or False
False
A crystal of solid NaCl is placed into an aqueous NaCl solution. It is observed that most, but not all, of the crystal dissolves. This means the original solution was saturated. True or False
False
Addition of a solute will cause in increase in the boiling point of a liquid. True or False
True
Solute-solute and solvent-solvent interparticle attractions must be overcome in order for a solute to dissolve in a solvent. True or False
True
Aqueous solutions of 0.1 M KCl and 0.1 M CaCl2 would have the same freezing point. True or False
False
Equal volumes of two solutions of the same molarity (but different solutes) contain the same number of grams of solute. True or False
False
Calculate the percent by mass concentration of a solution prepared by adding 0.562 g NaCl to water to make a total volume of 60.0 ml?
%(m/v) = (mass solute (g)/ Volume solution (ml)) * 100 = (0.562 g / 60.0 ml) * 100 = 0.937 %(m/v)
A 150.0 ml sample of solution contains 50.0 g LiBr. What is the molarity of this solution?
M = moles / L ; 50.0 g * 1 mol / 86.84 g = 0.576 moles LiBr; 0.576 moles / 0.1500 L = 3.84 M
You need 25.0 g CaCl2 for a reaction mixture. How much of a 0.825M solution of CaCl2 should you add?
25.0 g * 1 mol / 111.1 g = 0.225 moles CaCl2 needed ; 0.225 moles * 1 L / 0.825 moles = 0.273 L (273 ml)
How would you make 500.0 ml of a 0.155M NaBr solution using a 1.75M stock solution?
Cs * Vs = Cd * Vd ; 1.75M * Vs = 0.155M * 500.0ml, Vs = (0.155M * 500.0ml) / 1.75M ; Vs = 44.3 ml ; Take 44.3 ml of the stock solution and add water to make the final volume of 500.0 ml.
Calculate the osmolarity of a 0.622M CsF2 solution.
osmo = molarity * # particles ; CsF2 disassociates into 3 particles ; osmo = 0.622M * 3 = 1.87 osmo
A 25.0 ml aliquot of alcohol was added to 235.0 ml water to create a 251.6 ml solution. What is the percent-by-volume concentration of the alcohol solution?
25 ml / 251.6 ml * 100 = 9.93 %(v/v)
A vial contains a 7.50 % (m/v) solution. How many milliliters would you remove to get 0.550 grams of the solute?
0.550 g * 100 ml / 7.5 g = 7.33 ml
For the reaction: N2 + O2 ---> 2 NO2 The concentrations at equilibrium for the species participating in the reaction are: [N2] = 0.0013M, [O2] = 0.0024, [NO2] = 0.0065. What is the equilibrium constant?
Keq = [N2]*[O2] / [NO2]2 = (0.0013M)*(0.0024) / (0.0065)*(0.0065) = 0.074