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 Matte

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 3000 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 the four: diethyl ether, ethyl alcohol water or ethylene glycol, has the weakest intermolecular forces? Justify your answer.

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 smallest density at STP? How does density relate to molar mass? Calculate the densities to support your answer. Which would be the best to use to fill a lighter than air balloon? Explain your answer.

Show a sample calculation.

Compound N₂ He CO₂

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 H_2O 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.

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 H_2O 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.