Post-Lap Questions 1. Two negatively charged ions were measured, chloride and bi
ID: 478181 • Letter: P
Question
Post-Lap Questions
1. Two negatively charged ions were measured, chloride and bicarbonate. Which is higher concentration in the bottled- water sample? To answer this question from a chemical viewpoint, you will need to compare molarities.
2. Using your results, what is the ratio of the bicarbonate molarity to the combined molarity of calcium + magnesium? If the calcium/magnesium and bicarbonate all came from limestone dissolved in the water, then the bicarbonate molarity should be exactly twice that of the calcium +magnesium molarity. How closely do your results agree with this prediction?
3. The pH of water for human consumption should be close to neutral. How closely does your bottled-water sample compare with this goal?
4. Check the labels on the bottled waters that you studied. Were they merely treated, or were they purified in some way? If so, list the method(s) used. What was the specific goal of the treatment? See sections 5.11 and 5.12 of your textbook for help.
5. Optional (this question is more challenging.) the text shows a label from one brand of bottled water. For the positive ions that are listed, calculate the total molarity of all positive iron charges. (keep in mind that an iron such as calcium, Ca+2, has two positive charges.) Do the same thing for the negative irons, (If sulfate, SO42-, is present, it has two negative charges.) How well does the sum of the positive charge molarity equal the sum of the negative charge molarity?
Calcium and Magnesium
Average molarity 353.33 mole/liter
Calculated ppm of Ca+Mg 1060 mg/L
Chloide
Average molarity 414.166 mole/liter or 414.17
Calculated ppm of Ca+Mg 1242.5 mg/L
Trial # 1 2 3 well number 35 37 34 Drops of water 20 20 20 Drops of AgNO3 35 37 34 Molarity of Ca+ Mg 350 370 340Explanation / Answer
A) looking at the data above let's first calculate the moles of bicarbonate. It would be double of what we found for calcium and magnesium
353.33 X2 = 706.66 moles which is definatly more than the moles of chloride ions in water that is 414.166 moles
B) Ratio of bicarbonate : Ca + Mg = 2:1. to establis these results relevant experimantal data is also neede for bicarbonate ions. the molarity so, calculated should be taken ratio with Ca+Mg
C)as it has lot of bicarbonate ions so, pH would be alkaline and no more neutral.