University:
Carleton College
Course:
CHEM 122 | Introduction to Chemistry
Academic year:

2023
Views:

210

Pages:

5
Author:

StellarStrategist

Solutions Homework 1. What is the solvent and what is the solute in MgF2(aq)? Solute: Solid - MgF2(s) Solvent: Water - H2O(l) 2. What ions will the following compounds break into: a. CaCl2: Ca2+ and 2Cl- b. NaOH: Na+ and OH- c. MgSO4: Mg2+ and SO4^2- d. Al2(SO4)3: 2Al3+ and 3SO4^2- 3. DRAW what is happening at the molecular level when each of the following is dissolved in water: KI(aq): K+ and I- ions separated in water CaO(aq): Ca2+ and O2- ions separated in water Na2S(aq): 2Na+ and S2- ions separated in water KNO3(aq): K+ and NO3- ions separated in water Mg(OH)2(aq): Mg2+ and 2OH- ions separated in water 4. What is the general solubility rule? Using that rule, what do you know is true about the polarity of oil? Hint: think of an oil/water mixture. 1 Won't be on quiz 5. Draw molecules in the boxes below to help understand concentration. Less concentrated solution: Fewer molecules in the solution More concentrated solution: More molecules in the solution 6. What is the difference between a concentrated and dilute solution? Concentrated solution: More moles of solute per liter of solution Dilute solution: Less moles of solute per liter of solution 7. Describe how to make a solution. Be sure to state what the name of the glassware that is used to make a solution. Won't be on quiz 8. Describe how to dilute a solution. Add more solvent (water!) 9. Describe at least two ways to make a substance dissolve faster. Won't be on quiz 10. How is osmosis related to the concentration of a solution? Think of the gummy bear lab. Won't be on quiz 11. Define the following terms: a. Saturated solution: A perfect amount of solute dissolved into a solution b. Supersaturated solution: More than typically possible solute dissolved into a solution c. Unsaturated solution: There can easily be more solute dissolved into a solution 12. Explain why salt is thrown on icy roads in the winter. Be specific about what is happening at the molecular level. Won't be on quiz 13. What happens to the boiling temperature of a substance when the amount of solute increases? Won't be on quiz Solubility Chart List the following solutions as saturated, unsaturated, or supersaturated: a. 70 g of CaCl₂ at 30°C: Unsaturated b. 50 g of KCl at 60°C: Supersaturated c. 20 g of KNO₃ at 30°C: Unsaturated d. 30 g of K₂Cr₂O₇ at 50°C: Saturated The temperature must be at least 50°C to dissolve 90 g of KNO₃ into 100 g of water. Why is Ce₂(SO₄)₃ different than all of the other compounds on the solubility chart? In general, the solubility of a salt increases as temperature increases, except for Ce₂(SO₄)₃. I have 20 grams of KCl dissolved into 100 g of water at 70°C. About how many more grams of KCl can be dissolved in the water to make it a saturated solution? About 30 g more. Molarity/Problems Fill in the equation circle: M = mol/L What is the concentration of a solution when 0.77 moles of NaCl is dissolved into water to make 1.2 L of solution? M = mol/L = 0.77 mol / 1.2 L = 0.64 M A 250 mL solution is made with 0.50 moles of KBr. What is the molarity of the solution? M = mol/L = 0.50 mol / 0.25 L = 2 M What is the volume of a 0.25 M solution that contains 2.2 moles of solute? 0.25 M = 2.2 mol / x x = 8.8 L