Use Burgandy color scantron to answer the questions. Students are expected to wo

Question

Use Burgandy color scantron to answer the questions. Students are expected to work independently (group discussions are encouraged) Your EXAM-1 is expected to be of similar questions. So, it is extremely important that you know how to solve similar problems. The temperature of a specific amount of gas in a scaled container changes from 20.0 degree C to 40.0 degree C. If the volume remains constant, the pressure will change from 740 mmHg to 370 mmHg. 791 mmHg. 693 mmHg. 370 mmHg. 1480 mmHg. For an ideal gas, which two variables are directly proportional to each other (if all other conditions remain constant)? P and V P and n P and T 2 only 2 and 3 only 1 and 2 only 1 only 3 only A given mass of gas occupies a volume of 4.00 L at 60 degree C and 550 mmHg. Which of the following mathematical expressions will yield its temperature at 3.00 L and 650 mmHg? 60 degree C Times 4.00 L/3.00 L Times 650 mmHg/550 mmHg 333 K Times 4.00 L/3.00 L Times 650 mmHg/550 mmHg 333 K Times 3.00 L/4.00 L Times 650 mmHg/550 mmHg 333 K Times 3.00 L/4.00 L Times 550 mmHg/650 mmHg 333 K Times 4.00 L/3.00 L Times 550 mmHg/650 mmHg A gas occupies a volume of 4.25 L at 850 mmHg and 65.0 degree C. Which of the following mathematical expressions will yield its volume at STP? 4.25 L Times 760 mmHg/850 mmHg Times 273 K/338 K 4.25 L Times 760 mmHg/850 mmHg Times 298 K/338 K 4.25 L Times 760 mmHg/850 mmHg Times 338 K/273 K 4.25 L Times 850 mmHg/760 mmHg Times 273 K/338 K 4.25 L Times 850 mmHg/760 mmHg Times 338 K/273 K Which conditions of P, T, and n, respectively, are most ideal? high P, low T, high n high P, high T, high n low P, high T, low n low P, low T, low n low P, high T, high n

Explanation / Answer

Solution:- (1) Initial temperature, T1 = 20.0 + 273 = 293K

final temperature, T2 = 40.0 + 273 = 313K

Volume is constant....

Initial pressure, P1 = 740 mmHg

final pressure, P2 = ?

we know that, at constant volume, pressure is directly proportional to the kelvin temperature.

P1/T1 = P2/T2

P2 = P1T2/T1

let's plug in the values...

P2 = 740 mmHg x 313K/293K = 790.5 = 791 mmHg

So, correct choice is (B) 791 mmHg.

(2) Ideal gas equation is....

PV = nRT

for P we could arrange the equation as...

P = nRT/V

This means P is directly proportional to n and T and inversely proportional to V.

So, the correct choice is (B) 2 and 3 only.

(3) V1 = 4.00L, T1 = 60 + 273 = 333K, P1 = 550 mmHg

V2 = 3.00L, P2 = 650 mmHg, T2 = ?

This is based on combined gas law equation...

P1V1T2 = P2V2T1

for T2 we could rearrange it as...

T2 = P2V2T1/P1V1

Let's plug in the calues...

T2 = 333K x (3.00L/4.00L) x (650 mmHg/ 550 mmHg)

So, the correct choice is (C).

(4) V1 = 4.25L, P1 = 850 mmHg, T1 = 65.0 + 273 = 338K

STP means standard temperature and pressure. So,

T2 = 273K and P2 = 760 mmHg, V2 = ?

It is again combined gas law equation so let's rearrange the equation, P1V1T2 = P2V2T1 for V2.

V2 = P1V1T2 / P2T1

V2 = 4.25L x (850 mmHg/760 mmHg) x (273K/338K)

So, the correct choice is (D).

(5) Ideal gas law are based on the assumptions that gas atoms have no volume and the attraction forces are negligible and they bounce like ping pong balls freely. Both of these are not the true assumptions but we use these since the effects are less.

If the pressure is infinite then the ideal gas would not take up space but in actual atoms do have volume so this is not possible. Hence, a gas is more ideal if the pressure is lower.

We know that kinetic energy is directly proportional to the temperature. So, higher temperature means the greater kinetic energy and so the atoms would be moving very fast. If they atoms are not moving then there atoms have time for inter atomic intercations but if the temperature is high then they don't have sufficient time for these interactions.

If we have an ideal gas then we could fill infinite n into a finite container but since the atoms have their own volume so it is not possible to fit infinite n into a finite container and hence the value of n should be lower.

So, Low P, high T, low n.

Hence, the correct choice is (C). Low P, high T, low n.

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