AnsLabExp13&
Monday, September 16, 2013
7:46 PM
1.
1,135 L of O2 are in a container at STP. Calculate the number of moles.
2.
0.673 moles of N2 are in a container at STP. Calculate the volume in mL.
3.
Write the ideal-gas equation and give the units for each term when R =
0.0821 L-atm/K-mol: Equation: _________________________________
a.
Units of P =
b.
Units of V=
c.
Units of T =
4.
Write the ideal-gas equation and give the units for each term when R =
62,400 mL-mmHg/K-mol: Equation: _________________________________
a.
Units of P =
b.
Units of V=
c.
Units of T =
5. Show by mathematical equations how one can determine the molar mass (MM) of a volatile liquid
by measurement of the pressure, volume, temperature, and mass of the liquid.
If 0.80 g of a gas occupies 295 mL at 25 degrees Celsius and 680 mmHg of pressure, what is the
molar mass (MM) of the gas?
Exp 13 5 6 Page 1
A sample of gas of mass 2.82 g occupies a volume of 639 mL at 27 degrees
Celsius and 1.00 atm pressure. What is the molar mass of the gas?
8.
What is the density of He at STP? Why do helium-filled balloons rise in air (the density of air is
about 1.2 g/L)
9.
What volume in mL will 6.5 g of CO2 occupy at STP?
10.
A mixture of cyclopropane gas and oxygen is used as an anesthetic. Cyclopropane contains
85.7% C and 14.3% H by mass:
a.
Calculate the empirical formula of cyclopropane.
b.
At 50.0 degrees Celsius and 0.984 atm pressure, 1.56 g cyclopropane has a volume of 1.00 L.
Determine the molar mass of cyclopropane.
Exp 13 5 6 Page 2
c.
From all the information above, determine cyclopropane’s molecular formula (true formula).
11.
CH4 + 2 O2 --> 2 H2O + CO2
If 2.5 L of CH4 is burned at STP, what volume of O2 is required for complete combustion? If CH4 is the
limiting reactant, what volume of CO2 is produced?
12.
Oxygen (O2) is diatomic and has the molar mass of 32.00 g/1 mol. Using this information,
calculate the density of O2 at STP:
a.
Using the ideal gas law (PV = nRT at STP)
b.
Using the molar mass and molar volume of O2 (MM = DRT/P at STP)
Exp 13 5 6 Page 3
c.
How do the densities compare?
13.
HCl?
How many grams of zinc chloride could be formed from the reaction of 7.96 g of zinc with excess
Zn(s) + 2 HCl(aq) --> ZnCl2(aq) + H2(g)
14.
Air bags in automobiles inflate when sodium azide, NaN3, rapidly decomposes to its component
elements: 2 NaN3(s) --> 2 Na(s) + 3 N2(g)
a.
How many moles of N2 are formed by the decomposition of 2.50 moles of NaN3?
2 NaN3(s) --> 2 Na(s) + 3 N2(g)
b.
How many grams of NaN3 are required to form 6.00 g of N2 gas?
2 NaN3(s) --> 2 Na(s) + 3 N2(g)
Exp 13 5 6 Page 4
15.
Soda-lime glass (Na2CaSi6O14) is prepared by fusing sodium carbonate, Na2CO3; limestone,
CaCO3; and sand, SiO2. The composition of the glass varies, but the commonly accepted reaction for its
formation is: Na2CO3(s) + CaCO3(s) + 6SiO2 à Na2CaSi6O14(s) + 2 CO2(g)
Using this equation, how many kilograms of sand would be required to produce enough glass to make
5000 total wine glasses that each weigh 400-g per bottle.
Na2CO3(s) + CaCO3(s) + 6SiO2 --> Na2CaSi6O14(s) + 2 CO2(g)
Exp 13 5 6 Page 5
16.
After reviewing the “Ideal Gas Law” pre-lab discussion on pp140-141 and Procedure B (pp
141-142) answer the following questions:
a.
If an insufficient amount of volatile liquid had been used, how would this have affected the
value of the experimental molar mass?
b.
What are the major sources of error in your determination of the molar mass?
c.
If the flask is not thoroughly wiped dry, how would this affect the molar mass?
d.
Water has a boiling point of 100. Degrees Celsius. Isobutyl alcohol has a b.p. of 108 degrees
Celsius. How would you modify the procedure used in this experiment to determine the molar mass of
isobutyl alcohol?
1. Using the data table below, calculate the Vapor Density & Molar Mass of 2-Propanol.
Exp 13 5 6 Page 6
18.
The density of 2-Propanol is 60.11g/mol. Using the calculation above and the given information, calculate the
percent error.
Exp 13 5 6 Page 7