Question

I have the answer to all of these, so can you just explain why those are the correct answers?

4. Which of the following does NOT necessarily affect the theoretical effusion) speed of a gas? A. Temperature C. Molar mass D. Kinetic Energy E. Effusion speeds are always the same 5. Which of the following will constant)? ncrease the pressure the most (assume all other varilables remain pressure A. Cutting the volume to a quarter (V4) C. Tripling the temperature (3) D. Doubling the number of moles (2) E. Cutting the number of moles to a half (1/2) there converse as wen 6. Consider a liquid and its vapor (gas) above it. Which best explains why the liquid remains liquid but some vapor is also present. A. Liquids molecules are heavy and gases moleculesanelight. C. Liquid molecules have different shapes than gas molecules which favor Interactions D. Liquid molecules are wet while gas molecules are dry E. None of the above id molecules interact favorably with each other and gas molecules have freedom. con Rgurati on avaiable eas: Freedom, acces sible space 7. Consider a pot of water that is currently boiling. Which of the following is FALSE? If the atmospheric pressure were to suddenly decrease, the water would stop bolling C. The equilibrium vapor pressure above the water is equal to atmospheric pressure D. If you put your hand over the boiling water, vapor will condense on your hand and would A. If the atmospheric pressure is 1.00 atm then the temperature of the water is 100 °CS. most likely hurt if you left it there for long enough E. All of the above are true T+ PiF the pressure wound +0 drop, so will the temperature

Answer 1

1- With increase in temperature, the kinetic energy of molecule increases. Thus they start moving with freater speed and vice-versa.

• With increase in mass of the molecule its speed decreases and vice-versa.
• Kinetic energy of a molecule is itself the speed of molecule.
• But the pressure of a gas itself arises due to the collision of molecules with each other and with the wall of the container. After the speed of a molecule changes, its collision changes, so as the pressure exerted by them changes. Pressure itself cant affect the movement of molecules like others ( temp, mass etc) Thus pressure has no effect on the speed of molecules of a gas.

2- If you reduce the volume of a cotainer and the number of molecules remains still the same, then there will be more molecules per area. We know pressure (P) = Force per Area. Now the Area decreases amd force (i.e the kinetic energy increases- Because due to lesser space, the molecules have more collision). Hence the overall pressure increases.

Dropping the temperature, speed of molecules decreases, thus collision decreases, hence force decreases, Hence here pressure cant be increased.

Tripling the temp, the speed increases, but since volume remains the same, a smaller increase in force only, doesnt affect the pressure much to increase.

Cutting the number of moles will decrease the collision. Thus pressure will decrease.

3- Generally a liquid exist as gas or vapour at its vapour pressue. i.e the pressure of the liquid is equal to the pressure of the surrounding. In this state, the gas molecules aquire greater mobility and moves freely. Thus at the top surface, there would be invariably some molecules with high energy due to their random motion. Therefore, they would begin to escape the liquid since nothing prevents them to do so. This is called evaporation. The liquid would continue to evaporate till any more evaporation occur that lead to again liquidification of the gas molecules. This gas pressure is known as vapor pressure of the liquid, and is equal to maximum pressure in which the substance can remain in gas phase at that temperature.

4- Boiling point is the point at which vapour pressure equals atmospheric pressure. In a liquid, some particles always have enough energy to escape to the gas phase. Gaseous particles are also returning to the liquid. The vapour pressure is the pressure exerted by the gas when the amount of particles leaving the liquid equals the amount of particles entering the liquid .

As temperature increases, more particles have enough energy to escape to the gas phase. This increases the vapour pressure. When the vapour pressure equals atmospheric pressure, the liquid boils.

Now if the atmospheric pressure decreases, then the required vapour pressure also decreases simultaneously. But boiling will still take place. Because the temperature of a liquid is always low that it cant evapourate itself. Thus anyhow it need heat to start boiling, then evapourating at equal pressure with atmosphere. Now lowering atmospheric pressure, the boiling point of water decreases (i.e it will nedd less temperature to boil), but will still boil to evapourate. So that it can go into its vapour state.

Thus with increasing or decreasing the vapour pressure, it has nothing to do with Boiling of water. It can only increase or decrease the Boiling Point.