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Announcements

• Lon-Capa Homework #7 due next Wednesday

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From your textbook (A&J)

• Chapter 4 The Property of Gases (p.133)

• What Do We Need to Know Already

– “We need to be familiar with SI units (Appendix 1B) and the concepts of force and energy (Section A). This chapter also extends the techniques of reaction stoichiometry (Sections L and M)

• If you need to catch up on the basics,

– A worksheet on gases will be available to download (in Lon-Capa) for practice

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The reaction used in the deployment of automobile airbags

is the high-temperature decomposition of sodium azide, NaN3,

to produce N2 gas. How many liters of N2 at 1.15 atm and

30.0 °C are produced by decomposition of 45.0 g NaN3?

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Example - Stoichiometric Relationships with Gases

2Na(s) + 3N2(g) 2NaN3(s)

Example

A 12.5 L Scuba diving tank is filled with a heliox mixture containing 24.2 g He and 4.32 g O2 at 298 K.

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Given: Mass He = 24.2 g Mass O 2 = 4.32 g V = 12.5 L

Need to find: He = ? O2 =? Phe = ? PO2= ? Ptotal =?

Calculate the mole fraction and partial pressure of each component in the mixture. What is the total pressure of the tank?

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Ptotal = 𝑛𝑡𝑜𝑡𝑎𝑙𝑅𝑇

𝑉

the mole fraction () = 𝑛𝑖

𝑛𝑡𝑜𝑡𝑎𝑙 =

𝑃𝑖

𝑃𝑡𝑜𝑡𝑎𝑙

Ptotal = P1 + P2 + P3 + …..= 𝑛1𝑅𝑇

𝑉+ 𝑛2

𝑅𝑇

𝑉+ 𝑛1

𝑅𝑇

𝑉+ …

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