HW3_New.wpd
10/21/10
CHM 2045
THIRD
PROBLEM SET
INSTRUCTOR: DON SWIETER
OFFICE: K223
PHONE: 3955303
QUESTIONS ABOUT GASES
1.
Convert the following to the indicated units.
a.
543 torr to atm
b.
1.75 atm to mm Hg (torr)
c.
43.2 L to mL
d.
1.004 g/mL to g/L
e.
20 °C to K
f.
100 K to °C
2.
To convert a pressure reading in mm Hg taken at sea level at the north pole in January to torr, would
you add or subtract? Explain.
2
3.
A sample of H gas occupies a volume of 1.18 L at 760 torr.
a.
What volume will the gas occupy at 800 torr?
b.
What volume will it occupy at 0.526 atm?
c.
What is the pressure if the volume is doubled?
4.
A sample of He gas occupies a volume of 100 mL at
S
23 °C.
a.
What is the volume if the temperature is increased to 60 °C?
b.
At what temperature in Celsius will the sample volume be 154 mL?
c.
What is the volume if the temperature is doubled?
5.
A 0.250 mol sample of Ar occupies a volume of
400 mL.
a.
What volume will 1.25 mol occupy?
b.
How many moles are there in 320 mL?
c.
What is the volume if the number of moles is doubled?
6.
What is the pressure exerted by a sample of gas if the original temperature is quadrupled, the
number of moles of sample is cut in half, and the volume is tripled?
2
7.
What is the volume occupied by 35.2 g of N (g) at 35 °C and 741 torr?
8.
A 25.0 L cylinder contains 36.6 g He at 10 °C.
How many grams of He must be released slowly to
reduce the pressure to 1.75 atm while maintaining the temperature at 10°C?
9.
If 100 mL of Y weighs 0.316 g at STP, calculate the molecular weight of Y.
3
10.
Ozone (O ) is an allotrope (different form of an element) of oxygen.
a.
Calculate the density of ozone gas at STP.
b.
Calculate the density of ozone at 25 °C and 700 torr.
11.
Gas, Z, is found to be 9.93% C, 58.64% Cl and 31.43% F by mass.
If 100 mL of Z has a mass of
0.540 g at STP, determine the empirical formula, the molar mass and the molecular formula for Z.
3
12.
Hydrogen gas and nitrogen gas react under suitable conditions to form NH (g).
a.
Write a balanced equation for this transformation.
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2
2
b.
How many liters of N are needed to combine with 3.0 L of hydrogen at STP?
3
3
c.
How many liters of NH can be produced?
How many moles of NH ?
2
2
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d.
If 10.0 g of H and 4.0 g N are reacted at STP, how many liters of NH can be formed?
2
2
13.
Consider a mixture of 96.0 g O and 140 g N at a pressure of 800 torr in a rigid container.
O
2
a.
What is
×
?
b.
Calculate the partial pressure of N ?
2
2
N
c.
If 12.0 g He are added to this bulb, what is the partial pressure of N ?
What is
×
?
2
3
4
14.
When HCl (g) reacts with NH (g) at laboratory conditions, a white crystalline solid (NH Cl) is
formed. The equation for this reaction is:
3
4
NH (g) + HCl (g)
ssd
NH Cl (s)
Now imagine that some HCl (g) is introduced into the end of a thin glass tube (1.00 m long) and
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at the same time some NH (g) is introduced into the opposite end of the tube.
a.
Will the solid form in the middle of the tube? If not, toward which end will it form? Explain.
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 Fall '11
 WEINSTEIN
 Chemistry, pH

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