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Laredo Community College
Science Department
CHEM 1411
Practice Test Chapter 3 Newton 1
Part I. Multiple Choice
Circle the letter of the BEST answer on the test here. When you have finished, use a #2 pencil (provided)
and completely darken the letter on the Scantron form which corresponds to your choice. If you make a
mistake, erase the wrong answer completely. Each question is worth 3 points.
- In a balanced equation, what is balanced?
(A) atoms (B) moles (C) molecules
(D) atoms and molecules (E) moles and atoms
The value of Avogadro’s number is mol
(A) 2.179 x 10
(B) 2.998 x 10
(C) 6.626 x 10
(D) 6.022 x 10
(E) 9.109 x 10
- The formula for methanol is CH 3
OH. This means that, in methanol,.
(A) for every 100 atoms of carbon there are 300 atoms of hydrogen and 100 hydroxide ions.
(B) for every gram of hydrogen there are twelve grams of carbon.
(C) for every twelve grams of carbon there are sixteen grams of oxygen.
(D) the compound is 33% oxygen by mass.
(E) the compound is 50% hydrogen by mass.
- The molar mass (to the nearest whole number) of anhydrous iron(II) sulfate, FeSO 4
, is
grams per mole.
(A) 104 (B) 152 (C) 248 (D) 336
(E) 400
- A sample of Fe 2
O
was found to contain 10.2 g of iron. How many moles of iron are there in
the sample?
(A) 0.180 (B) 0.360 (C) 2.00 (D) 3.
Atomic Masses
H 1.0 g mol
-
C 12.0 g mol
-
N 14.0 g mol
-
O 16.0 g mol
-
- The expression “one mole of copper(II) sulfide” refers to the mass of.
(A) copper(II) sulfide needed to occupy one liter of solution
(B) solid copper(II) sulfide needed to occupy 22.4 L at STP.
(C) copper combined with sulfur in one molecule.
(D) copper(II) sulfide in grams equal to one formula molar mass
(E) one molecule (in grams) of copper(II) sulfide
- Why is this equation incorrect? Mg 3
+ N
Mg 3
N
(A) Some of the subscripts are incorrectly used.
(B) The equation is not balanced.
(C) The valence of the nitride ion is incorrect.
(D) The valence of the magnesium ion is incorrect.
(E) The coefficient of N 2
is incorrect.
- Which procedure can be used to demonstrate experimentally that the reaction below obeys the
Law of Conservation of Matter?
2 Mg + O 2
2 MgO
(A) Take a mass of 1.0000 g of Mg ribbon, burn it in pure O 2
, and compare the mass of the
product with the original mass of the Mg.
(B) Show that the sum of 2 atomic molar masses of Mg plus 1 molar mass of O 2
is equal to 2
molar masses of MgO.
(C) Determine the mass of a sealed flash-bulb containing magnesium and oxygen, ignite the
mixture, cool, and compare the final mass of bulb plus contents with the original mass of the
bulb plus contents.
(D) Burn 1.0000 g of Mg ribbon in a tall beaker filled with air, scrape out all of the MgO formed,
and compare with the original mass of the Mg.
- The chemical equation 2 CO 2
2 CO + O
informs us that.
(A) when 2 mol of CO 2
decompose, less than 2 mol of CO will be formed and the quantity of O 2
formed will be less than 1 mol
(B) only under special conditions will 2 mol of CO 2
yield 2 mol of CO and l mol of O 2
(C) carbon dioxide decomposes, but that the relative amounts of CO 2
, CO, and O 2
involved in
the reaction are a function of conditions.
(D) regardless of conditions, the decomposition of l mol of CO 2
will yield l mol of CO and
mole of O 2
(E) the tendency of CO 2
to decompose is equal to the tendency of CO and O 2
to combine
- What is the percentage of oxygen by mass in (NH 4
PO
(A) 100 % (B) 100 %
(C) 100 % (D) 100 %
- A compound of which halogen is used in etching glass?
(A) astatine (B) iodine (C) bromine
Molar Masses (g mol
CO
44.0 H
O 18.
(A) C
H
(B) C
H
(C) C
H
(D) C
H
Part II. Short Answer
Answer each question in the space provided on. The point value of each question is shown with the
question. Use the back of the page if you need more room.
- Balance the following chemical equations using small whole number coefficients. Be sure to
include a coefficient in each blank. (6)
a) C 6
H
12
O
6
+ O
2
CO
2
+ H
2
O
b) H 3
PO
**_4
(PO
4
2
+ H
2
O
c) (NH 4
2 Cr 2
O
7 Cr 2
O
3
+ N
2
+ H
2
O
Show all work, including units, for the word problem. Record your answers to the proper number of
significant figures.
Partial credit may be earned, but all work (with appropriate units) must be shown in order to receive full
credit for the problem. No credit will be given for an answer only. Circle your final answers.
- Laboratory tests have confirmed the presence of the nerve agent Sarin inside a roadside bomb
which exploded in Baghdad. The elemental composition of Sarin is given in the table below.
The molecular weight of the compound is 140 amu.
a) What is the empirical formula of Sarin? (4)
b) What is the molecular formula of Sarin? (2)
34.29 % C
7.19 % H
22.84 % O
13.56 % F
22.11 % P
C 12.
amu
H 1.
amu
O 16.
amu
