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The Chemical Formulas and Equations Test consists of 15 questions. Correct answers are found through links located at the end of each question.

The answer section is formatted for on-screen use, not printing, and will waste a lot of paper if printed directly.

Have a fun learning experience!
Question #1: The formula weight of C6H12O6 is
(A). 180

 6 of C =  6 X 12 u = 72 u
12 of H = 12 X  1 u = 12 u
 6 of O =  6 X 16 u = 96 u

72 + 12 + 96 = 180 u
Question #2: The number of sulfur atoms in Al2(SO4)3 is
(A). 3

The formula tells us there are 3 SO4 polyatomic ions bound to 2 aluminum atoms. There is 1 sulfur atom in a SO4 polyatomic ion, so there are 3 sulfur atoms in 3 SO4 polyatomic ions.
Question #3: The formula for a compound is given as C2H2. This is a (an)
(B). molecular formula.

C2H2 is a covalent compound, so the formula might be molecular. Since it is not the simplest whole number ratio (which would be CH), then the formula is molecular.
Question #4: What number should be in front of H2SO4 in the equation below?
(C). 3

There are 3 SO4 polyatomic ions and there are 6 hydrogen atoms on the right side. A coefficient of 3 in front of the H2SO4 will balance both the SO4 and the hydrogen atoms.
Question #5: The equation below is balanced by placing what number in front of the carbon dioxide?
(A). 4

There are 4 C and a total of 2 + 12 = 14 O in the reactants. There are 6 O in the water product, leaving a need for 4 C and 14 - 6, or 8 O in the products. Placing a coefficient of 4 in front of the carbon dioxide will balance the C and O atoms.
Question #6: Which of the following equations is balanced?


Inventory the number of each kind of atom on both sides of each equation and you will find that only (D) is balanced.
Question #7: Which of the following represents a replacement reaction?


A replacement reaction follows the general form of XY + Z yields XZ + Y or XY +A yields AY + X. Equation (B) is the only one that approaches this general form. Zinc is above copper in the activity series shown in figure 12.13 (page 289), so you can predict that a replacement reaction would occur.
Question #8: Which of the following represents a combination reaction?


A combination follows the general form of X + Y yields XY.
Question #9: Which of the following represents an ion exchange reaction?


In general, an ion exchange reaction has the form AX + BY yields AY + BX where one of the products removes ions from the solution as a precipitate, a gas, or water. This is a reaction between an acid and a base, which forms a salt and water.
Question #10: Which of the following would not result in a reaction?











Reacting solid gold with a water solution of hydrochloric acid might be an ion exchange reaction, but gold is below hydrogen in the activity series so no reaction occurs.



























































Question #11: If the atomic mass of oxygen is 16 u and Avogadro's number is 6.02 X 1023 particles per mole, then one mole of ozone, O3, contains






(A). 6.02 X 1023 molecules.



An amount of a substance that contains Avogadro's number of atoms, ions, molecules, or any other chemical unit is defined as a mole of the substance. Thus a mole of O3 contains Avogadro's number of molecules, which is 6.02 X 1023 molecules.
























































Question #12: How many moles of hydrogen atoms are present in 1 mole of H2O?





(B). 2



Every mole contains Avogadro's number of particles and 2 times Avogadro's number of hydrogen atoms combines with Avogadro's number of oxygen atoms to form Avogadro's number of water molecules. There are therefore two moles of hydrogen in each mole of H2O.




























































Question #13: The mass of 6.02 X 1023 atoms of gold (Au) is






(B). 197 g



The mole concept and Avogadro's number provide a relationship between numbers and masses. The atomic weight of gold is 197 u, so the gram-atomic weight of gold is 197 grams. A gram-atomic weight is one mole of an element, so the mass of 6.02 X 1023 atoms of gold is 197 grams.































































Question #14: How many moles of oxygen atoms are present in 1 mole of H2O?






(B). 1



Every mole contains Avogadro's number of particles. Since 2 times Avogadro's number of hydrogen atoms combines with Avogadro's number of oxygen atoms to form Avogadro's number of water molecules. There is therefore one mole of oxygen in each mole of H2O.






























































Question #15: The formula weight of carbon dioxide, CO2 is






(B). 44 u



1 of C = 1 X 12 u = 12 u

2 of O = 2 X 16 u = 32 u 


32 + 12 = 44 u
























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