Basic Chemistry Lab
Laboratory Exercise 2
The instructor will identify five groups of students. Each group will be responsible for performing the activities listed below and completing the exercise assignments. Results from each group will be shared by recording information in a posted version of Table 1.
Exactly 0.01 mole of each of the assigned compounds and 15 g of the soils, listed in Table 1, will be available in labeled plastic cups.
1. Add 10-ml of distilled water to each cup containing a chemical compound, intermittently stir or swirl the contents until it dissolves or 5 minutes have passed. Note, in the appropriate column of Table 1, if the compound dissolves (S = dissolves; I = did not all dissolve).
2. Add an additional 90-ml of distilled water to each of the cups containing chemical compounds. For compounds that did not initially dissolve, continue to stir or swirl again until it dissolves or 5 minutes have passed. Again note whether or not the compound dissolved.
3. Measure the solution pH for each of the compounds and record the result in Table 1.
4. Add 15 ml of distilled water to each of the soils, stir intermittently, wait about 5 minutes, measure and record the pH in Table 1.
5. Add 1 ml of standard acid to solutions (chemical compounds and soils) that were basic in step 3 and 4, and 1 ml of standard base if the solution or soil was acidic. Stir, wait a minute or two, measure and record the pH. Identify the buffer capacity of the mixture as low (L = pH change 5 or more units), medium (M = 2 to 5 units) or high (H = less than 2 units).
6. Write the cation and anion (include charges) of each compound in the last two columns of Table 1.
nutrient availability to plants is governed by
Unlike weakly buffered solutions, the strongly buffered solutions are resistant to small additions of a strong acid/base.
Acid/base reaction: acid (donates a proton) and a base (accept a proton) react to form a salt and water. During the reaction, a proton is donated by the acid to the base to yield water. The remaining ions form a salt.