AP Chemistry Summer Homework Chapter 3
____/150pts
Name:
1. (5pts) An element consists of the following isotopes:
Isotope
1
2
Percent
19.78
80.22
The average atomic mass is
Mass
10.013 amu
11.019 amu
amu calculated to two decimal places.
The element is
2. (15pts) a) How many atoms of carbon are present in 1.0 g of Na2CO3?
b) How many atoms of carbon are present in 1.0 g of CH3CO2H?
c) How many atoms of nitrogen are present in 25.0 g of Ca(NO3)2?
3. (30pts) a) Vitamin B12, cyanocobalamin, is essential for human nutrition. Its molecular
formula is C63H88CoN14O14P.
A lack of this vitamin in the diet can lead to anemia.
Cyanocobalamin is the form of the vitamin found in vitamin supplements. What is the
molar mass of vitamin B12?
b) How many moles of B12 molecules are present in 250 mg vitamin B12?
c) What is the mass of 0.75 mol vitamin B12?
d) How many atoms of hydrogen are in 1.0 mol of vitamin B12?
e) What is the mass of 1.0 × 106 molecules of vitamin B12?
f) What is the mass (in grams) of one molecule of vitamin B12?
4. (20pts) Arrange the following substances in order of increasing percent of phosphorus.
Na3PO4
PH3
P4O10
(NPCl2)3
5. (5pts) A 0.4230 g sample of impure sodium nitrate (contains sodium nitrate plus inert
ingredients) was heated, converting all the sodium nitrate to 0.2440 g of sodium nitrite
and oxygen gas. Determine the percent of sodium nitrate in the original sample.
6. (10pts) a) A compound with molar mass 51.00 g/mol has the following composition:
Na
C
O
43.4%
11.3%
45.3%
Determine the empirical formula.
b) A compound with molar mass 180.2 g/mol has the following composition:
C
H
O
60.0%
4.48%
35.5%
Determine the molecular formula.
7. (15pts) Vanillin, the primary flavoring molecule in vanilla, is a molecule that contains
the elements carbon, hydrogen, and oxygen. Complete combustion of a 1.05 g sample
of vanillin produced 2.43 g carbon dioxide and 0.50 g of water. (Hint: The law of
conservation of mass tells you that the amount of carbon in the product, carbon dioxide,
is the same amount of carbon in the reactant, vanillin. The amount of hydrogen in the
product, water, is the same amount of hydrogen in the reactant, vanillin. There are
example problems that are similar to this one in the chapter. )
Find the empirical formula for vanillin.
8. (25pts) The production capacity for acrylonitrile (C3H3N) in the United States is over 2
billion pounds per year. Acrylonitrile, the building block for polyacrylonitrile fibers and a
variety of plastics, is produced from gaseous propylene, ammonia, and oxygen:
2C3H6(g) + 2NH3(g) + 3O2(g)
2C3H3N(g) + 6H2O(g)
a) Assuming 100 % yield, determine the mass of acrylonitrile which can be produced
from the mixture below (Hint: this is a limiting reactant problem)
Mass
322. g
5.00 x 102 g
1.00 x 103 g
Reactant
propylene
ammonia
oxygen
b) Using the balanced reaction: 2C3H6(g) + 2NH3(g) + 3O2(g)
What mass of water is formed from your mixture?
Mass
322. g
5.00 x 102 g
1.00 x 103 g
Reactant
propylene
ammonia
oxygen
2C3H3N(g) + 6H2O(g)
c) Using the masses of the reactants listed above and the balanced equation:
2C3H6(g) + 2NH3(g) + 3O2(g)
2C3H3N(g) + 6H2O(g)
Calculate the mass (in grams) of each reactant after the reaction is complete (excess):
9. (15pts) Over the years, the thermite reaction has been used for welding railroad rails, in
incendiary bombs, and to ignite solid fuel rocket motors. The reaction is
Fe2O3(s) + 2Al(s)
2Fe(l) + Al2O3(s)
a) What mass of iron(III) oxide must be used to produce 88.34 g of iron?
b) What mass of aluminum must be used to produce 13.92 g of iron?
c) What is the maximum mass of aluminum oxide that could be produced along with
13.92 g iron?
10. (10pts) Hexamethylenediamine (C6H16N2) is one of the starting materials for the
production of nylon. It can be prepared from adipic acid (C6H10O4) by the following
overall reaction:
C6H10O4(l) + 2 NH3(g) + 4 H2(g)
C6H16N2(l) + 4 H2O(l)
a) What mass of hexamethylenediamine can be produced from 146.9 g adipic acid?
b) What is the percent yield if 94.62 g hexamethylenediamine is made from 146.9 g
adipic acid?