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1. P A = P T x Y A P A = partial pressure of any gas A P T = total pressure of g

ID: 699986 • Letter: 1

Question

1.

PA = PT x YA

PA = partial pressure of any gas A

PT = total pressure of gas

YA = mole fraction of gas A

PT = PN2 + PO2 =0.1 atm + 0.4 atm = 0.5 atm

YO2 = PO2/PT = 0.4 atm / 0.5 atm = 0.8

YO2 + YN2 = 1 { sum of all the mole fractions is always one}

YN2 = 1 - YO2 = 0.2

also YN2 = nN2 / nT { nN2 can be found by this }

nN2 = total no. of oxygen moles

nT = total no. of moles of all the gases

also

YO2 = nO2 / nT

nT = 2 mol / 0.8 = 2.5 mol

nT = nN2 + NO2 {nN2 can be found from this also}

nN2 = 2.5 mol - 2 mol = 0.5 mol

2.

from reaction equation we see that 2 mol H2O2 forms 1 mol O2(g)

total moles of O2 in chamber = 1 mol + 2 mol = 3 mol

total moles of gases = O2 + N2 = 3 + 0.5 = 3.5 mol

as the temperature is constant

P1V1/n1T1 = P2V2/n2T2

where P , V , n ,T represents pressure , volume ,no. of moles and temperature respectively

subscript shows the state of process

P1 = original total pressure = 0.5 atm

V1 = V2 = constant as it is rigid container

T1 = T2 given constant temperature

n1 = 2.5 mol

n2 = 3.5 mol

0.5 atm x V1 / (T1 x 2.5 mol) = P2 x V1 / (T1 x 3.5 mol)

P2 = 0.7 atm

Explanation / Answer

Hydrogen peroxide decomposes slowly at room temperature, according to the following balanced chemical equation You place 2.0 mol of H,O, (1) in a rigid flask which already contains 2.0 mol of O, (g) and an unknown quantity of N2 (g). Before the reaction takes place the partial pressure of oxygen in the flask is 0.40 atm and the partial pressure of N2 (g) is 0.10 atm. Answer both of the next two questions hased on heo(01. 03) 1. Before you added H,O, () to your flask, what was the mole fraction of nitrogen gas? a. 0.050 b. 0.10 c.0.20 d. 0.25 02. If the reaction goes to completion and the temperature stays constant, what is the final total pressure in the flask? a. 0.30 atm b. 0.50 atm 0.70 atm 0.90 atm d.