Introduction to Chemistry formative exercise answers about molecular compounds

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Due Wednesday 11:59 PM May , 2000

Quiz 7: Solids, Liquids & Gases: States of Matter

Short essay questions

1. 12 points

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A barometer is shown in the illustration. What is the approximate indicated air pressure in mm Hg? What is this in atmospheres? Would this be classed as HIGH pressure? The atmosphere is typically 20% oxygen and 80% nitrogen. What is the partial pressure of oxygen at this pressure? What is the advantage of placing a carbon monoxide poisoning victim in a hyperbaric chamber ? Justify your answers.

2. ----- 8 points

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A balloon initially had a volume of 5000 liters at 20^oCelsius and 1.0 atmospheres. What is the volume of the balloon at 10^oCelsius and a pressure of 1.0 atm? Show set ups for calculations.

Describe what happens to the volume of a gas when the gas is cooled and the pressure is kept constant? What happens to the gas in terms of kinetic molecular theory when the temperature decreases?

3. ----- 8 points

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Explain what would happen to the boiling point and freezing point for water if there was no such thing as hydrogen bonding. Tell what other forces exist between water molecules besides hydrogen bonding. Justify your answer.

4. ----- 8 points

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Which of these: diethyl ether, ethyl alcohol water or ethylene glycol, has the strongest intermolecular forces? Justify your answer using the vapor pressure information..

If possible tell what the approximate boiling point for each liquid would be if the opposing pressure was lowered to 300 torr (300 mm Hg)?

Compound diethyl ether ethyl alcohol water

Boiling point at 300 torr ------------------------------- ------------------------------- --------------------

What generally happens to the observed boiling point when the opposing pressure is increased? What relationship is there between this behavior and the sterilizer autoclaves used in health care clinics?

5. 9 points

Which of the following gases has the greatest density at STP? How does density relate to molar mass? Calculate the densities to support your answer. Which would have the greatest tendancy to sink to the ground? Explain your answer.

Show a sample calculation.

Compound C_{6H6
, benzene} He , helium CO_2,carbon dioxide

Density at STP ----------------- ----------------- -----------------

Molar mass ----------------- ----------------- -----------------

True false 1 point each

1. A body centered cubic unit cell like copper metal has only one "atom" in the cell.

2.

The average kinetic energy of gas molecules depends on Kelvin temperature.

3. The body centered cubic unit cell packs atoms more efficiently than simple cubic.

4. Molecules like water, H₂O interact through dipole-dipole forces and hydrogen bonding.

5. Hydrogen bonding can exist when molecules have any of the following bonding combinations. H-F, H-O, H-N.

		EXTRA CREDIT 4 points
		What graphic in the webiste was most helpful?
		What graphic or animation would you like to see added?

last revised May 18, 2000

3.	-----	8 points
-----		Explain what would happen to the boiling point and freezing point for water if there was no such thing as hydrogen bonding. Tell what other forces exist between water molecules besides hydrogen bonding. Justify your answer.

		True false 1 point each
1.		A body centered cubic unit cell like copper metal has only one "atom" in the cell.
2.		The average kinetic energy of gas molecules depends on Kelvin temperature.
3.		The body centered cubic unit cell packs atoms more efficiently than simple cubic.
4.		Molecules like water, H₂O interact through dipole-dipole forces and hydrogen bonding.
5.		Hydrogen bonding can exist when molecules have any of the following bonding combinations. H-F, H-O, H-N.