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Dalton’s LawDalton’s Law

John DaltonJohn Dalton1766-18441766-1844

Chapter 12 : Day 4

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DALTON’S Law• PARTIAL PRESSURES

• Total pressure equals the sum of the parts

• INDEPENDENT of composition

Scuba d5 c9Scuba d5 c9

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Dalton’s Law of Partial Dalton’s Law of Partial PressuresPressures

What is the total pressure in the flask?What is the total pressure in the flask?

PPtotaltotal in gas mixture = P in gas mixture = PAA + P + PBB + ... + ...Therefore, Therefore,

PPtotaltotal = P(H = P(H22O) + P(OO) + P(O22) = 0.48 atm) = 0.48 atm

Dalton’s Law: total P is sum of Dalton’s Law: total P is sum of PARTIALPARTIAL pressures. pressures.

2 H2 H22OO22(liq) ---> 2 H(liq) ---> 2 H22O(g) + OO(g) + O22(g)(g)

0.32 atm 0.32 atm 0.16 atm 0.16 atm

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Mole Fraction• Partial pressure is proportional to the mole fraction

of any gas

a = __na _____ = na_

na + nb + nc ntotal

a = __Pa _ = na_

Ptotal ntotal

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WSPg 61

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