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1. A mixture of three gases is shown in the figure at right. The total pressure

ID: 1038573 • Letter: 1

Question

1. A mixture of three gases is shown in the figure at right. The total pressure in this system is 950 torr. (a) Determine the partial pressure of gas C in the mixture. (b) Determine the mole-fraction of gas B in the mixture. (c) Which of the following would cause a decrease in the mole-fraction of B in the mixture: Choose one more A is added to the mixture ) more B is added to the system ) the temperature of the system increases (d) Which of the following would cause a decrease in the partial pressure of C in the mixture: Choose one ( some He is added to the mixture some C reacts with B to make CB ) the temperature of the system increases (e) Clearly defend your answer to (d) in 20 words or less. Use complete sentence(s).

Explanation / Answer

Total no of particles = 17

a) no of particles of C = 8

Mole fraction of C = 8/17

Partial pressure=mole fraction × total pressure = (8×950)/17 = 477.06 torr

b) mole fraction of B = no of particles/ total no of particles = 5/17

c) adding more A will decrease the mole fraction of B as the total no of particles in the system increases.

d) some C reacts with B to form CB

e) partial pressure is independent of the presence of other gases. If temperature increases partial pressure will increase.

If some C were to react with B to form CB, no of particles of C would decrease with corresponding decrease of mole fraction and thus the partial pressure.