Conceptual Review
What are all of the ways of expressing concentrations that were mentioned in lecture?
Molarity, Mass percent, Volume percent, Mass-volume percent, parts per billion, and parts per billion.
What is the molarity of a solution that contains 10.0 grams of Silver Nitrate that has been dissolved in 750 mL of water?
0.078 M AgNO3
How many grams of potassium carbonate are needed to make 200 mL of a 2.5 M solution?
69.1 g
What does it mean for a solution to be concentrated?
Concentrated solutions have more solute per unit volume.
You want to create a 0.25 M Potassium Chloride solution. You mass 5.00 grams of Potassium Chloride. How much water is needed?
0.27 L or 270 mL
How many liters of 4 M solution can be made using 100 grams of lithium bromide?
3.47 L
What does it mean for a solution to be dilute?
Dilute solutions have less solute per unit volume.
What is the percentage by mass of the solution from problem 100? (Problem 100: What is the molarity of a solution that contains 10.0 grams of Silver Nitrate that has been dissolved in 750 mL of water?)
1.32 AgNO3
What is the concentration of an aqueous solution with a volume of 450 mL that contains 200 grams of iron (II) chloride?
3.51 M
Can concentrated solutions become dilute and visa-versa? Why or why not?
Concentrated solutions can be made dilute by adding more solvent. Dilute solutions can be made more concentrated by adding more solute, or by removing (selectively) more solvent.
How many mL of hydrogen peroxide are needed to make a 8.5% solution by volume of hydrogen peroxide if you want to make 450 mL of solution?
38 mL H2O2
What is the concentration of a solution with a volume of 2.5 liters containing 660 grams of calcium phosphate?
0.85 M
What is the Formula Mass? What is the Molecular Mass? Can both Covalent and Ionic compounds have both a formula mass and molecular mass? Why or why not?
For covalent substances, the formula represents the numbers and types of atoms composing a single molecule of the substance; therefore, the formula mass may be correctly referred to as a molecular mass.
Ionic compounds are composed of discrete cations and anions combined in ratios to yield electrically neutral bulk matter.
The formula mass for an ionic compound is calculated in the same way as the formula mass for covalent compounds: by summing the average atomic masses of all the atoms in the compound’s formula.
Keep in mind, however, that the formula for an ionic compound does not represent the composition of a discrete molecule, so it may not correctly be referred to as the “molecular mass.”
A sample of an industrial waste water is analyzed and found to contain 26.8 ppb Zn2+. How many grams of zinc could be recovered from 1.86x10^3 kg of this waste?
0.0498 or 4.98x10-2 g Zn2+
Too much fluoride ion in drinking water can cause the following undesirable effects: tooth discoloration. The EPA's Secondary Maximum Contaminant Level for fluoride ion in drinking water is 2.00 mg/L. If 1.12x10^4 liters of water in a storage tank contains 4.75 grams of F-, what is the contaminent level in ppm? (Assume that the density of impure water is 1.00 g/mL). Is this level acceptable base on EPA guidlines?
0.424 mg/L F- ; Yes, it is acceptable because 0.424 mg/L F- < 2.00 mg/L.