17.11: Worksheets for Chapter 17
Copy and distribute the lesson worksheets. Ask students to complete the worksheets alone or in pairs as a review of lesson content.
Concentration by Percent Mass Worksheet
CK-12 Foundation Chemistry
Name______________________ Date_________
The definition of percent mass concentration is the ratio of the mass of solute divided by the total mass of the solution and multiplied by 100 to convert to a percentage.
Example: What is the percent concentration by mass of a solution formed by dissolving of ethanol, , in of water?
Solution: percent by mass =
Example: If the density of a by mass solution in water is , how many grams of are present in of the solution?
Solution: We can multiply the volume times the density to the mass of the of solution and then take of the mass of the solution to get the mass of the potassium nitrate.
Exercises
- If of are dissolved in of water, what is the concentration of the silver nitrate by mass percent?
- How many grams of are present in of a in water solution?
- How many grams of water are present in the solution in question #2?
- The density of a by mass solution of in water is . How many grams of are required to prepare of this solution?
- The density of pure water is . What is the concentration gy percent mass of a solution prepared by dissolving of in of water?
- A solution is prepared by dissolving of acetone, , in of water. The density of the solution is . What is the percent concentration of acetone by mass?
- A solution of in water has a density of . How many grams of phosphoric acid are present in of this solution?
Mole Fraction and Molality Worksheet
CK-12 Foundation Chemistry
Name______________________ Date_________
Mole Fraction
The definition of mole fraction is the ratio of the moles of solute divided by the total moles of the solution.
Example: What is the mole fraction of ethanol in a solution prepared by dissolving of ethanol, , in of water?
Solution:
Molality
The definition of molality is the ratio of the moles of solute divided by the kilograms of solvent.
Example: What is the molality of a solution prepared by dissolving of ethanol, , in of water?
Example: A solution of in water has a density of . What is the mole fraction of in this solution and what is the molality?
Solution: We can choose a sample volume of this solution and get the mass of it by multiplying the volume times the density. Suppose we choose a sample.
Exercises
- What is the mole fraction of in a solution that has of dissolved in of water?
- What is the molality of the solution in question 1?
- The density of a by mass solution of in water is . What is the mole fraction of in this solution?
- What is the molality of the solution in problem 3?
- What is the molality of a solution prepared by dissolving of in of water?
- How many grams of beryllium chloride would you need to add to of water to make a solution?
- What would be the mole fraction of in the solution in problem 6?
- A solution is prepared by dissolving of acetone, , in of water. The density of the solution is . What is the molality of this solution?
- What is the mole fraction of acetone in the solution in problem 8?
Molarity Worksheet
CK-12 Foundation Chemistry
Name______________________ Date_________
The definition of molarity is the ratio of the mols of solute divided by the volume of the solution.
Example: What is the molarity of a solution prepared by dissolving of in sufficient water to produce of solution?
Solution:
Example: What volume of solution will contain of ?
Exercises
- What is the molarity of a solution in which of is dissolved in of solution?
- How many grams of ammonia, are present in of solution?
- How many milliliters of solution is necessary to contain of ?
- How many liters of solution is required to contain of ?
- What mass of ammonium phosphate is needed to make of solution?
- What is the molarity of a solution prepared by dissolving of in of solution?
- How many grams of glycerine, , are needed to make of solution?
- A test tube contains of solution. How many grams of calcium carbonate are in the tube?
Dilution Worksheet
CK-12 Foundation Chemistry
Name______________________ Date_________
The process of dilution involves increasing the amount of solvent in a solution without changing the amount of solute. For example, you could dilute of solution by placing the solution in a graduated cylinder and adding water until the solution reached the line in the graduate. The original solution contained of before it was diluted and therefore, it also contains of after the dilution. In the process of dilution, the amount of solute never changes. The amount of solvent, the total volume of the solution, and the concentration change but the amount of solute remains the same.
For a solution whose concentration is expressed in molarity, the moles of solute can be calculated by multiplying the volume in liters times the molarity.
For the moles of solute in the original solution, or . After the solution has been diluted, the moles in the final solution can be calculated with . Since the mols do not change during dilution,
In the dilution problems you will be given, for the most part, three of the four variables or ways to find three of the four variables and you will asked to calculate the fourth variable.
Example: How many milliliters of solution are necessary to prepare of solution?
Solution:
Exercises
- of solution is diluted to a final volume of . What is the concentration of the final solution?
- of concentrated hydrochloric acid was diluted to of solution. What was the concentration of the original concentrated solution?
- What volume of is needed to prepare of ?
- If of is diluted to , what is the final concentration?
- To what volume must you dilute of to produce a solution that is ?
- Solution A is of . Solution B is prepared by diluting solution A to a new volume of . Solution C is produced by taking of solution B and diluting it to . What is the molarity of solution C?
Colligative Properties: Solution Vapor Pressure Worksheet
Colligative properties are those properties of a solution that depend on the number of particles of solute present in the solution, and not on the chemistry nor the mass of the particles. That is, the chemical behavior and the molar masses of urea, , and glucose, , are very different, but the colligative properties of a solution of urea will be exactly the same as the colligative properties of a solution of glucose.
The colligative properties of solutions include vapor pressure lowering, boiling point elevation, freezing point depression, and changes in osmotic pressure. The changes in these properties are dependent entirely on the concentration of particles of solute in the solution. It must be noted that ionic solutes dissociate when dissolved in water and therefore, add more particles to the solution than a substance that does not dissociate in water.
Vapor Pressure Lowering
The vapor pressure of a solution can be calculated from the individual vapor pressures of the components (solute and solvent) and the mole fractions of each component. Raoult's Law is an expression of the relationship.
Example: What is the vapor pressure, at , of a solution produced by dissolving of acetone, , in of water? The vapor pressure of pure acetone at is of and the vapor pressure of pure water at is of .
Solution: of acetone is and of water is
Therefore, the mole fractions in this solution are acetone and water.
In this case, the vapor pressure of the solution is higher than the vapor pressure of the solvent. That is due to the fact that acetone is a volatile (weak intermolecular forces of attraction) and therefore, evaporates readily. When we refer to vapor pressure lowering, we are referring to solutions in which the solute is non-volatile. When the solute is a solid, it can be generally be assumed that the solute is non-volatile.
Suppose we are making a solution of glucose in water. Glucose is a non-volatile, solid solute whose vapor pressure at room conditions is so small that it is negligible compared to the vapor pressure of water. When we substitute the values for a glucose solution into Raoult's Law, the second term (the one for the solute) is essentially zero because the vapor pressure of the pure solute is essentially zero.
If the second term in this equation, , becomes zero, then for a solution with a non-volatile solute, Raoult's Law becomes:
This is Raoult's Law for solutions whose solute is a non-volatile.
Example: What is the vapor pressure, at C, of a solution produced by dissolving of glucose, , in of water? Glucose is non-volatile and the vapor pressure of pure water at is of .
Solution: of water is and of glucose is
Therefore, the mole fraction of water in this solution is . We do not need to calculate the mole fraction of glucose because it isn't needed in Raoult's Law for non-volatile solutes.
In this case, and in all cases of non-volatile solutes, the vapor pressure of the solution is less than the vapor pressure of the pure solvent.
Exercises
- If of sodium chloride is added to of water at , what will be the vapor pressure of the resulting solution in kPa? The vapor pressure of pure water at is
- of the non-volatile solute glucose, , is dissolved in of water at . IF the vapor pressure of water at is , what is the vapor pressure of the solution?
- Glycerin, , is a non-volatile, non-electrolyte solute. If of glycerin is dissolved in of ethanol at , what is the vapor pressure of the solution? The vapor pressure of pure ethanol is at
- The vapor pressure of hexane, , at is . The vapor pressure of benzene at the same temperature is . What will be the vapor pressure of a solution of of hexane with of benzene?
Colligative Properties: B.P. Elevation and M.P. Depression Worksheet
When a non-volatile, solid solute is added to a solvent, the boiling point of the solution will be higher than the boiling point of the solvent, and the melting point of the solution will be lower than the melting point of the solvent. The size of the boiling point elevation and the melting point depression are colligative properties, that is, they are dependent not on the chemistry of the solute but only on the number of solute particles present in the solution.
The formula used to calculate boiling point elevation is , where is the increase in the boiling point, is the molality of the solute, is the boiling point elevation constant, and is the van't Hoff factor.
The boiling point elevation constant, , is an experimentally determined constant for the solvent. Each solvent will have its own and these values are determined in the laboratory and listed in reference tables. For example, the boiling point elevation constant for water is . As the molality of the solution increases, the boiling point of the solution increases by for each increase of in the molality.
The van't Hoff factor is the ratio between the actual concentration of particles produced when the substance is dissolved, and the concentration of the molecules dissolved. For most non-electrolytes dissolved in water, the van't Hoff factor is essentially 1. For most ionic compounds dissolved in water, the van't Hoff factor is equal to the number of discrete ions in a formula unit of the substance. For example, a glucose solution that is will have a particle concentration that is also because glucose molecules do not dissociate. A sodium chloride solution, on the other hand, since it dissociates into two ions will have a particle molality of . The van't Hoff factor, , is the number of ions that the molecule will dissociate into when dissolved. Sometimes, in concentrated solutions, an ionic substance does not dissociate and therefore, the value of will not be exactly equal to the apparent number of ions produced. In such cases, the value of must also be determined experimentally. If you are not given an actual value for in the problem, assume that is the number of ions apparently produced per molecule. This is true in most dilute solutions.
The formula used to calculate melting point depression is , where is the decrease in the melting point, is the molality of the solute, is the melting point depression constant, and is the van't Hoff factor.
The melting point depression constant, , is an experimentally determined constant for the solvent. Each solvent will have its own and these values are determined in the laboratory and listed in reference tables. For example, the freezing point depression constant for water is . As the molality of the solution increases, the melting point of the solution decreases by for each increase of in the molality.
Example: What is the boiling point of a glucose solution in water? Glucose is a non-volatile, non-electrolyte solute. for water =
Solution:
Since the boiling point of the pure solvent was , the b.p. of the solution is
Example: What is the melting point of a solution in water? Sodium chloride is a non-volatile solute that dissociates in water. for water =
Solution: (Since produces two ions in solution, )
Since the melting point of the pure solvent was , the m.p. of the solution is
Exercises
- What is the melting point of a solution produced by dissolving of in of water. for water = .
- What is the boiling point of a solution produced by dissolving of in of water. for water = .
- Which solution will have higher boiling point: a solution containing of in of water or a solution containing of in of water?
- When of an unknown, non-volatile, non-electrolyte is dissolved in of water, the boiling point of the solution is . What is the molar mass of the unknown?
- How many grams of (anti-freeze, a non-electrolyte) must be added to of water to reduce the melting point to ?
- The melting point constant for benzene is . The normal melting point of benzene is . What is the melting point of a solution of of (a non-electrolyte) in of benzene?
- Assuming dissociation, what is the boiling point of a solution of of in of water?
Reactions Between Ions in Solution Worksheet
CK-12 Foundation Chemistry
Name______________________ Date_________
For the following five reactions (all reactants are in water solution):
- Write and balance the molecular equation indicating the state of each reactant and product.
- Write the total ionic equation.
- Identify the precipitate.
- Identify the spectator ions.
- Write the net ionic equation.
1. iron (III) chloride + sodium hydroxide
Balanced molecular equation _____________
Total ionic equation _____________
Precipitate = _____________ Spectator ions = _____________
Net ionic equation _____________
2. barium chloride + silver nitrate
Balanced molecular equation _____________
Total ionic equation _____________
Precipitate = _____________ Spectator ions = _____________
Net ionic equation _____________
3. magnesium sulfate + potassium phosphate
Balanced molecular equation _____________
Total ionic equation _____________
Precipitate = _____________ Spectator ions = _____________
Net ionic equation _____________
4. copper (II) nitrate + calcium hydroxide
Balanced molecular equation _____________
Total ionic equation _____________
Precipitate = _____________ Spectator ions = _____________
Net ionic equation _____________
5. sodium chromate + strontium nitrate
Balanced molecular equation _____________
Total ionic equation _____________
Precipitate = _____________ Spectator ions = _____________
Answers to Worksheets
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