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Lesson 3 Lab: Pipetting and Self-Inflating Hydrogen Balloons


Begin by viewing the following Thinkwell video

(a) (1 pts) What is a pipette and for what is it used? Be specific.

(b) (1 pts) What is the difference between a graduated pipette and a volumetric pipette, and what is the specific function of each?

(c) (2 pts) What is the proper technique for using each of these instruments? What is the importance of the "meniscus" in this technique?

(d) (1 pts) Give a specific example of how you could use a pipette (if one were available), in your own daily life, and explain which type of pipette you should use in your situation and why.


Please watch the following Thinkwell video:

(a) (3 pts) First, the instructor violated several safety rules in this video. List and explain/discuss at least (3) safety rules he violated.

(b) (2 pts) Why did these balloons inflate? Write and discuss a balanced chemical equation for this reaction and use it to help explain your answer.

(c) (2 pts) What remained in the last (4th) flask (the one with the green balloon) at the end of the reaction? Why? What does this demonstrate with regard to limiting reactant?

(d) (2 pts) Why was the same amount of HCl kept in every flask? Why didn’t the instructor vary those amounts as well? Be detailed and specific in your answer. The

(e) (2 pts) Why did the 3rd flask balloon (the red one) inflate more than the 1st flask balloon (the purple one)? Incorporate the concept of limiting reagent in your answer.

(f) (4 pts) Suppose you ran this same reaction (using the balloon setup as seen in the video) on your own with two different flasks. In Flask A, you reacted 5.10 g Mg with 0.447 mol HCl. In Flask B, you reacted 24.21 g Mg with 0.998 mol HCl. Which ballon will inflate the most? Explain (in detail) why, showing all work.

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