CHEM120 Midterm: Chemistry Midterm 2

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limecrab895

29 Nov 2016

School

University of Waterloo

Department

Chemistry

Course

CHEM120

Professor

German Sciaini

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Document Summary

Partial pressure of a depends on number of moles of a. Total pressure depends on total number of moles of gas. Small amounts of gas are collected over water. Total pressure of gas inside inverted cylinder = atmospheric pressure. Gas collected is wet" mixed with water vapour. Partial pressure of water vapour depends only on temperature of water (found in table) Method of collecting gas only works if gas is not soluble (or does not react) in water. Two main assumptions: molecules are in constant random motion, average kinetic energy of molecules is proportional to the kelvin temperature. Lighter molecules travel faster than heavier molecules. Molecules escape from its container through an opening eg. air leaking from tire. Molecules of one gas mix amongst those of another eg. perfume sprayed in air. Real gases: pressure increases (and temperature decreases), deviations from ideal gas equation extent of deviations at given temperature depend on temperature and nature of gas.

Related Questions

3. A steel tank with a volume of 75.0 L contains 0.106 moles of He(g). Solve for the pressure this gas exerts, in atm, at a temperature of 15.0 deg. Celsius.

4. Hydrogen gas is collected over water at 22.0â by reacting zinc with hydrochloric acid according to the following equation. Zn(s) + HCl(aq) â ZnCl2(aq) + H2(g) The total gas pressure is 756.9 torr. The vapor pressure of water at this temperature is 19.8 torr. Solve for the pressure, in units of kPa, of the pure hydrogen gas.

5. _____ All of the following are postulates of the Kinetic Molecular Theory except:

a. Gas molecules are small compared to the volume of the container, their volume is considered negligible.

b. Gas molecules do not have attractive or repulsive forces toward one another.

c. Gas molecules are in constant, straight line motion, and do not change direction until colliding with something.

An instrument used to measure the pressure of a gas in a laboratory is called a barometer manometer sphygmomanometer spectrophotometer spectrometer The pressure of a gas in a container is1.85 atm and occupies a volume of 12.5 L If the original volume is reduced by hall at constant temperature, what would happen to the pressure? The pressure would ... double reduce by half remain the same On a hot summer day, you notice that a bag of chips left in your vehicle has inflated. As temperature increased, gas molecules .......... kinetic energy and the volume of gas inside the bag ....... Lost/increased gained/decreased lost/decreased gained/increased What mass of oxygen gas (O_2) is needed to fill a 585 L tank at STP? 0 835 kg 0.765 kg 0.417 kg Which of the following will cause the volume of an ideal gas to triple in value Raising the temperature from 25 degree C to 75 degree C at constant pressure. Lowering the absolute temperature by a factor of 3 at constant pressure. Lowering the pressure by a factor of 3 white the temperature stays constant. A 0.334 g sample of an unknown halogen occupies 109 mL at 398 K and 1.41 atm. What is the identity of the halogen? Br_2 F_2 C1_2 l_2 Define vapor pressure. partial pressure cf water in a Squid mixture partial pressure of wafer in a gases mixture condensation of water A mixture of 1.0 mol He and 1.0 mol No are at STP in a rigid container. Which of the following statements is TRUE Both gases have the same average kinetic energy. Both gases contribute equally to the density of the mixture under these conditions. Both gases have the same molecular speed. The following reaction is used to generate hydrogen gas in the laboratory Mg(s) + 2 HC1(aq) rightarrow MgC1_2(aq) + H_2(g) If 243 mL of gas is collected at 25 degree C and has a total pressure of 745 mm Hg. what mass of hydrogen is produced? Listed are vapor pressures at select temperatures: Listed are water vapor Pressures at select temperatures: 0.0144 g H_2 0.0717 g H_2 0.0190 g H_2 Which of the following compounds will behave LEAST like an ideal gas at low temperatures? He SO_2 H_2 N_2 F_2 A container Filed with neon and argon gas is 25.00% by volume neon. What is the partial pressure of argon it the total pressure inside the container is 5 500 atm? 412 5 atm 1.375 atm 4.125atm 28 5 L of an unknown gas has a mass of 55.92 g at STP. What is the identity of the unknown gas? CO_2 O_2 N_2 Explain what would happen to the following equilibrium upon the addition of more hydrogen gas? H_2O(g) + CO(g) doubleheadarrow H_2(g) + CO_2(g) producing more reactants producing more CO_2 equilibrium will not be attected For the following reaction, K_5 = 5.6 x 10^-6 (at 400 K): 2 NOC(g) doubleheadarrow 2 No_2(g) + C1_2(g) If [NOCI] = 0.0222 M, [CI_2] = 0.0222 M, [NO_2] = 0.989 M at once, which statement would be true? The rate of forward and reverse reaction are equal. Neither forward nor reverse reaction would occur. Rate of forward reaction would be taster. Rate of reverse reaction would be faster. K_c = 1.10 times 10^18 for CO(g) + 1/2 O_2(g) doubleheadarrow CO_2(g) Calculate the equilibrium concstant K_0 for the following CO_2(g) doubleheadarrow CO(g) + 1/2 O_2(g) 1.04 times 10^9 0.55 times 10^18 -1.10 times 10^18 9.09 times 10^19

Question 11 pts

Which general statement about gases is NOT correct?

The molecules of a pure gas are distributed evenly throughout the container.

Gases are much less dense than liquids or solids

Molecules in a gas mixture can form layers according to their densities

Gases can be compressed, even to the point of liquefaction

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Question 21 pts

Which example is the greatest pressure?

1.00 atm

101 kPa

760 mm Hg (= 760 torr)

All of the above pressures are equal.

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Question 31 pts

Which example is the greatest pressure?

850 mm Hg (= 850 torr)

1.5 atm

All of the above pressures are equal.

96 kPa

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Question 41 pts

Assuming all other variables are held constant, a graph of which of the following will NOT yield a straight line?

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Question 51 pts

A sealed vessel contains 0.250 mol of oxygen gas. Which of the following will result in a decrease in the pressure of the oxygen gas?

increasing the number of moles of oxygen

increasing the temperature of the vessel

increasing the volume of the vessel

adding some helium to the vessel

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Question 61 pts

According to Charlesâs law, which change will cause the pressure of a gas to double? Pressure and amount of gas are constant.

The temperature decreases from 650 K to 325 K.

The temperature of the sample decreases fromï¿½88 Â°C to 44 Â°C.

The temperature of the sample increases fromï¿½22 Â°C to 44 Â°C.

The temperature of the sample increases fromï¿½250 K to 500 K.

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Question 71 pts

Which set of units for P, V, and T can be used for combined gas law calculations?

torr, L, and Kelvins

tm, g/L, and Kelvins

atm, mL, and degrees Celsius

inches of mercury, g/mL, and degrees Celsius

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Question 81 pts

The vapor pressure of a gas is

the atmospheric pressure at which the boiling point is determined.

the pressure at a Kelvin temperature exactly two times the boiling point.

impossible to determine experimentally without knowing the temperature and volume.

the pressure above a gas sample when evaporation and condensation are balanced.

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Question 91 pts

In a chemistry experiment where CO2 is collected over water, the atmospheric pressure is 755 mm. The partial pressure of water at the temperature in the lab is 24.2 mm. What is the pressure of the CO2?

779 mm

731 mm

More information is needed to answer this question

755 mm

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Question 101 pts

Which statement is NOT true according to the kinetic molecular theory of gases?

Molecules undergo elastic collisions

Molecules move in straight-line paths.

Molecules of different gases have differentï¿½kinetic energies at the same temperature

Molecules occupy a negligible volume.

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