HT+Task+4

=**Water Test: Alkalinity I - Gathering the Data**= //Taken from Project Search - Chemical Parameters//

The alkalinity of water is a measure of its buffering capacity. The higher the value, the more acid can be neutralized, the more the water can resist a change in pH. Alkalinity of natural waters is primarily the result of bicarbonates but is expressed in terms of calcium carbonate (CaCO 3 ). Carbonates (CO 32- ) and bicarbonates are common to most waters since they are abundant in nature. However, if the bedrock of watersheds is lacking in carbonates and other buffering minerals, as in granite bedrock, alkalinity values will be low. The alkalinity of fresh waters is typically between 20 and 200 mg/l .In CT, where bedrock geology is largely granite schist and gneiss, alkalinity values are generally well below 100 mg/l.

Decreasing alkalinity over a period of years can have serious effects on the stream ecosystem, as well as downstream lakes and ponds. Gradual lowering of the pH can result in the disappearance of some aquatic species and a decline in the condition and reproductive rate of fish. Alkalinity levels are most critical in the spring when acidic snowmelt and surface run-off are greatest and many aquatic species are in the early and most susceptible phase of their life cycle.

The pH of water does not decline steadily with acid contamination. Buffering minerals moderate the decline to around pH 6.4. Below pH 5.5 very little buffering materials remain and the pH declines rapidly upon addition of acid. At about pH 4.5, the buffering capacity of the water is lost.

1.) What does the alkalinity of the water measure? 2.) If the river is highly alkaline, how well would it adapt to changes in pH? 3.) What are the three causes of the alkalinity of natural water? 4.) What range of alkalinity is freshwater typically found in CT? 5.) When are Alkalinity levels the most critical?
 * Prelab**

See attached Procedure 1.) What safety precautions do you need to take for this lab? 2.) What three chemicals will you use for the Alkalinity test?
 * Procedure**

1.) What was your Phenolphthalein (P) Alkalinity? 2.) What was your total (T) Alkalinity?
 * Data**

1.) What was your Hydroxide Alkalinity? 2.) What was your Carbonate Alkalinity? 3.) What was your Bicarbonate Alkalinity?
 * Analysis**

1.) Where there any difficulties in the lab? 2.) What might you do differently next time?
 * Conclusion**