Name: ______
Date: ______
Testing for Ions in Water
Introduction
Is all water pure? Water looks clear but it may contain small amounts of different chemicals. There could be traces of metals, salt or other types of ions. Is all water the same? If we have 3 types of water: taken from Lake Ontario, Northern’s Swimming Pool, and from a Natural Spring. Will they all have the same composition of trace elements and ions? Through this lab, we will investigate these questions.
[2 TI] NOTE: A good hypothesis is directly related to the introduction; it makes a prediction about the questions written there. The prediction must be falsifiable; meaning that it must be able to be proven true or false, it cannot be automatically true nor can it be automatically false and it cannot be something which cannot be determined. It should also have a rationale; a reason for making the prediction that way. A hypothesis does not have to make a correct prediction, just a reasonable one.
Procedure – Part One (Control Tests)
1) Put on goggles; this lab contains substances which are corrosive (Sodium Hydroxide) and which are severe skin irritants (Silver Nitrate & Barium Nitrate). Goggles must remain on for the entire duration of the lab; you have been warned.
2) Add 3 drops of each control solution (calcium nitrate, sodium chloride, and sodium sulfate) in three different wells to set up your spot plate like this:
3) Add 3 drops of the test solution, sodium hydroxide, to the 3 drops of calcium nitrate, sodium chloride, and sodium sulfate. Take great care when adding the drops to avoid contamination.
4) Follow Step 3 for each of the other test solution: silver nitrate and barium nitrate
5) Make observations against the background of a white sheet of paper to detect colour changes and against a black background to detect precipitates.
6) Dispose all used chemicals in the waste beaker. Rinse and dry the spot plate.
Observations – Part One Control Table [3 TI]
Test Solutions / Sodium Hydroxide / Silver Nitrate / Barium NitrateControl Solutions
Calcium Nitrate
Sodium Chloride
Sodium Sulfate
Part One Questions
1) What solution should you use to test for calcium? What will you see if calcium is present? [2 TI]
2) What solution should you use to test for chloride? What will you see if chloride is present? [2 TI]
3) What solution should you use to test for sulfate? What will you see if sulfate is present? [2 TI]
4) Why is it important to prevent contamination of the solutions? [2 TI]
5) Why is it important to dispose of these solutions in the waste beaker? [2 TI]
Procedure - Part Two (Water Sample Tests)
1) Similarly to part 1, add 3 drops of “Lake Ontario Water” into 3 different wells on a spot plate.
2) Repeat Step 1 for “Swimming Pool Water” and “Natural Spring Water”.
3) Add 3 drops of each of the test solutions (sodium hydroxide, silver nitrate and barium nitrate) to the three different water samples.
4) Record your observations in the chart provided.
5) Dispose of all chemicals into the waste disposal beaker. Clean your apparatus and return all chemicals to the front of the class.
Observations – Part Two Water Sample Table [3 TI]
Test SolutionsWater Sample
[2 TI] NOTE: A good conclusion clearly identifies if the prediction made in the hypotheses is correct. It justifies the conclusion with specific reference to the data collected.
Part Two Questions
1) What ion(s) were present in the “Lake Ontario” water? [1 TI]
2) What ion(s) were present in the “Swimming Pool Water?” [1 TI]
3) What ion(s) were present in the “Spring Water?” [1 TI]
4) Which sample of water do you think is the purest? Explain. [2 TI]
5) Do you think it is bad to drink water with ions in it? Justify your answer. [2 TI]
6) Write the correct chemical formulas for the compounds used in the lab. [6 KU]
Name / Formulaa) calcium nitrate
b) sodium chloride
c) sodium sulfate
d) sodium hydroxide
e) silver nitrate
f) barium nitrate
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