What is the partial pressure of argon in a mixture that contains of 0.054 g of A

Question

What is the partial pressure of argon in a mixture that contains of 0.054 g of Ar and 0.048 of N_2, and has a total pressure of 1504 mmHg? For each of the below processes, indicate whether energy is being transferred as either heat or work, and indicate the sign of q or w for the system. a. A ball is rolled up a steep incline, the ball is the system b. A cold pack is activated and applied to a sprained ankle, the cold pack is the system. c. A wax crayon bums in the presence of oxygen, the crayon is the system

Explanation / Answer

Q2.

partial pressure of Argon in a mix with:

m ar = 0.054 g

m N2 = 0.048 g

Ptotal = 1504 mm Hg

so..

mol of argon = mass/MW = 0.054/39.948 = 0.00135 mol of Ar

mol of n2 = mass/MW = 0.048/28 = 0.001714 mol of N2

total mol = 0.001714+0.00135 = 0.003064 mol

mol fraction of argon = mol of Argon / total mol = 0.00135/0.003064 = 0.4406

then

P-Argon = x-Ar * Ptotal = (0.4406)(1504) mm Hg = 662.6624 mm Hg of Argon

Q3

Assume

Q - W = dE

a)

ball being rolled up, it is moving, so work is being applied to the system, W = must be negative

b)

the cold pack is absorbing heat from the surrounding, so Q must be negative

c)

Wax burns, so it increases in temperature, Q increases, Also, Vapor is produced, so volume expands and Work is created, msut be negative

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