6.1 Test Review

Objective1: Describe factors affecting the process of dissolving and evaluate the effects that changes in concentration have on solutions.

  1. Review the role of science in societal issues. The role of science is to pursuer truth using the scientific method. The scientific method includes asking questions, setting up experiments, measuring, proposing conclusions based on observable data. Consider the role of science and its involvement in issues that deal with concentrations (public health, drinking water, water quality, air quality, etc.)
  2. Perform molarity calculations. You will be given a solution volume and a solute mass. Calculate the molarity. For example, what is the molarity of 25.0 grams of salt in 2.00 L of solution?
  3. Review decimals and their values. Which is the biggest number 0.1, 0.01, and 0.001? I haven’t taught you this yet, but parts per million is an easy concept. It is similar to percent. The only difference is percent is parts in a hundred parts. Parts per million is parts in a million parts. You may also calculate them like percents except instead of dividing the ratio and multiplying by 100, multiply by 1,000,000.

4/5 x 100 = 80%

4/5 x 1,000,000 = 800,000 parts per million (ppm)

  1. What happens when a solution forms? Consider different solutions like sugar water and salt water. What does the solution look like on the molecular level? Can you draw the sugar molecules mixing with the water molecules? How about the salt ions mixing with the water molecules? Review terms like solute, solvent, solution, mole, mixture, substance, particles, homogeneous, heterogeneous, dilute and concentrated. Can you see salt when it is dissolved in water?
  2. Make sure you review in the textbook how molar solutions are made. There is a nice graphic and explanation. What is the correct way to calculate and make a molar solution? Review how to convert mass in grams to moles so you can calculate molarity. What is the molar mass of C6H12O6? How many moles are in 36.0 grams of C6H12O6?
  3. Review molarity (moles/liter), molality (moles, kilogram), mole fraction (moles/total moles), ppm (parts per million), and normality (normality compares equivalents—you won’t have to know too much about this). We have not covered mole fraction but it is a simple concept. Mole fraction is simply the number of moles of solute compared to the total moles in the solution. Parts per million and parts per billion would be used to measure very low concentrations.
  4. Understand how to adjust components of a solution and maintain the concentration. How could you make Kool-Aid with only 1 cup of sugar instead of two? How much Kool-Aid would you use? What about water?
  5. What if you were asked molarity questions differently than you are used to? Can you solve moles given a molarity and a volume?
  6. What does the amount of solvent have to do with how concentrated a solution is? What about how dilute it is? What about solvent? How does it affect concentration and dilution?
  7. This is a tough one. What if you were given a solution concentration in molarity and you were asked how many moles are in 0.500 L of a 2.00 M (molar) solution? A 2.00 M solution has 2.00 moles per liter. If you only have 0.500 L then you only have 1.00 mol. Make sure you can try problems like this. Make some up on your own.
  8. Again, make sure you study parts per million. How many grams of lead would have to accumulate in 100 grams of blood to make a solution with a concentration of 0.1 ppm?