Question

A mixture of 14.0 grams of hydrogen, 84.0 grams of nitrogen, and 2.0 moles of oxygen are placed in a flask. When the partial pressure of the oxygen is 78.00 mm of mercury, what is the total pressure in the flask?

Answer 1

Total pressure in the flask : 468 mmHg

Further explanation  

Dalton's law of partial pressures states that the total pressure of a mixture of gases is equal to the sum of the partial pressures of the component gases  

Can be formulated:  

P tot = P1 + P2 + P3 ....  

The partial pressure is the pressure of each gas in a mixture  

For partial gas :

Pgas₁=x₁.P tot

x₁ = mole fraction of gas 1

mol of each gas :

H₂ = 14 g : 2 g/mol= 7 moles

N₂ = 84 g : 28 g/mol = 3 moles

O₂ = 2 moles

Total moles = 7+3+2= 12 moles

Partial pressure of O₂ :

$\tt P_{O_2}=x_{0_2}\times P_{tot}\\\\78~mmHg=\dfrac{2}{12}\times P_{tot}\\\\P_{tot}=\dfrac{78\times 12}{2}=468~mmHg$

Answer 2

The study of chemicals is called chemistry.

The correct answer is 468mmhg.

Dalton's law defined as partial pressures states that the total pressure of a mixture of gases is equal to the sum of the partial pressures of the component gases  

The formula is stated as follows:-

$P_{total} = P_1 + P_2 + P_3...$

The partial pressure is the pressure of each gas in a mixture. For partial gas is as follows :

$P_{gas}_1=X_1.P_{total}$

The $X_1$ defined as a mole fraction of gas 1

The mole of each gas is as follows:-

$H_2 = \frac{14}{2}= 7 molesN_2 = \frac{84}{28} = 3 molesO-_2 = 2 moles$

Total moles = $7+3+2= 12 moles$

The partial pressure  $O_2$ is as follows:-

$P_{total} = \frac{78*12}{2} =468mm$.

Hence, the correct answer is 468mmhg.

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