Question

A mixture of gases contains 8.94 g of N2, 3.61 g of H2, 2.17 g of NH3. If the total pressure of the mixture is 4.03 atm, what is the partial pressure of each component?Pn2=Ph2=Pnh3=

Answer 1

To solve this question we have to apply Dalton's Law.

Dalton's Law states that the total pressure of a mixture of gases is the sum of the partial pressures of each of the components of the mixture:

`P=P_1+P_2+P_3+...+P_n`

Also, that the partial pressure of a component of a mixture is the product of the molar fraction of the component times the total pressure of the mixture:

`P_i=y_1P`

To solve this problem the first step is to find the molar fractions of each of the components of the mixture. To do this we have to convert the given masses to moles using the corresponding molecular weights:

`\begin{gathered} 8.94gN_2\cdot(molN_2)/(28gN_2)=0.319molN_2 \\ 3.61gH_2\cdot(molH_2)/(2gH_2)=1.805molH_2 \\ 2.17gNH_3\cdot(molNH_3)/(17gNH_3)=0.128molNH_3 \end{gathered}`

Find the sum of this values to find the total number of moles in the mixture:

`N=0.319+1.805+0.128=2.252mol`

Divide the amount of moles of each component by the total amount of moles of the mixture to find each of the molar fractions:

`\begin{gathered} yN_2=(0.319)/(2.252)=0.142 \\ yH_2=(1.805)/(2.252)=0.802 \\ yNH_3=(0.128)/(2.252)=0.056 \end{gathered}`

Finally, apply Dalton's Law to find each of the partial pressures:

`\begin{gathered} PN_2=0.142\cdot4.03atm=0.572atm \\ PH_2=0.802\cdot4.03atm=3.232atm \\ PNH_3=0.056\cdot4.03atm=0.226atm \end{gathered}`