Dalton's Law

Chemistry Level 2

In chemistry and physics, Dalton's law (also called Dalton's law of partial pressures) states that the total pressure exerted by the mixture of non-reactive gases is equal to the sum of the partial pressures of individual gases. This empirical law was observed by John Dalton in $1801$ and is related to the ideal gas laws. If $1$ L of oxygen with a pressure of $3$ atm and $2$ L of nitrogen with a pressure of $6$ atm are mixed in a container with a volume of $3$ L as shown above, then what is the pressure of the gas mixture? (Assume that the temperature is constant.)

4.5 atm 5 atm 5.5 atm 9 atm

1 solution

Joem Camacho
Mar 5, 2014

Using partial pressures, (instead of moles, volume fraction is used.) so, we let ${ P }_{ TOTAL }=\quad { P }_{ { { O }_{ 2 } } }(\frac { { V }_{ { O }_{ 2 } } }{ { V }_{ TOTAL } } )+\quad { P }_{ { N }_{ 2 } }(\frac { { V }_{ { N }_{ 2 } } }{ { V }_{ TOTAL } } )$ . substituting the given values, we get ${ P }_{ TOTAL }=\quad 3.0atm\quad (\frac { 1L }{ 3L } )+\quad 6.0atm\quad (\frac { 2L }{ 3L } )\quad =\quad 5.0\quad atm$

Did the same!!

Tanya Gupta - 7 years, 3 months ago

His way complies to statements of Dalton's Law. From $P V = n R T = Constant$ , we can think that P is the magnitude under consideration while V is its quantity.

$P_1 V_1 + P_2 V_2 = Constant_1 + Constant_2 = Constant_3 = P_3 V_3$

3 $\times$ 1 + 6 $\times$ 2 = $P_3$ $\times$ 3 $\implies~ P_3 = \frac{ 3 + 12}{3} = 5$

This can be confirmed by:

3 $\times$ 1 + 3 $\times$ 1 = $P_3$ $\times$ 1 $\implies~ P_3 = \frac{ 3 + 3}{1} = 6$

This compliance agrees to Dalton's Law and also proven it.

Answer: $\boxed{5~atm}$

Lu Chee Ket - 5 years, 4 months ago

Dalton's Law

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