Chemistry (Chang), 10th Edition

Chapter 3: Mass Relationships in Chemical Reactions

Self Assessment A

1
Determine the number of moles of aluminum in 0.2154 kg of Al.
A)1.297 x 1023 mol
B)5.811 x 103 mol
C)7.984 mol
D)0.1253 mol
E)7.984 x 10-3 mol
2
How many phosphorus atoms are there in 2.57 g of P?
A)4.79 x 1025
B)1.55 x 1024
C)5.00 x 1022
D)8.30 x 10-2
E)2.57
3
How many grams of acetylsalicylic acid (aspirin, C9H8O4) are present in 1.32 x 10-2 mol of C9H8O4?
A)1.32 x 10-2 g
B)2.38 g
C)180.2 g
D)7.33 x 10-5 g
E)None of the above
4
Calculate the percent composition by mass of nitrogen in ammonium nitrate (NH4NO3).
A)0.175%
B)0.350%
C)17.5%
D)35.0%
E)42.5%
5
A compound with a percent composition by mass of 87.5% N and 12.5% H was recently discovered. What is the empirical formula of this compound?
A)NH2
B)N2H3
C)NH
D)N2H2
E)N2H
6
What is the coefficient for CO2 when the following chemical equation is properly balanced using the smallest set of whole numbers?

C4H10 + O2 ----> CO2 + H2O
A)1
B)4
C)6
D)8
E)12
7
What mass of copper(II) nitrate would be produced from the complete reaction of 45.6 g of copper, according to the chemical reaction shown below?

Cu + 2 AgNO3 ----> Cu(NO3)2 + 2 Ag
A)0.72 g
B)21.1 g
C)98.7 g
D)135 g
E)187 g
8
Calculate the number of moles of H2O formed when 0.200 mole of Ba(OH)2 is treated with 0.500 mol of HClO3 according to the chemical reaction shown below.

Ba(OH)2 + 2 HClO3 ----> Ba(ClO3)2 + 2 H2O
A)1.00 mol
B)0.600 mol
C)0.500 mol
D)0.400 mol
E)0.200 mol
9
Ammonia is produced industrially from the reaction of nitrogen and hydrogen. Write the balanced chemical equation for this reaction, and determine the largest mass of NH3 that could be produced from the reaction of 105 g of N2 and 15.0 g of H2.
A)28.4 g
B)42.2 g
C)63.8 g
D)84.5 g
E)128 g
10
In the Hall-Heroult process, anhydrous aluminum oxide is reduced to aluminum according to the chemical equation:

2 Al2O3 (s) ---> 4 Al (l) + 3 O2 (g)

Calculate the mass of aluminum oxide reacted if 385 g of Al was produced and the percent yield was found to be 89.3%.
A)814.6 g
B)215.6 g
C)1630 g
D)815 g
E)727 g
11
Which of the following is least helpful in balancing an equation?
A)Use a balance sheet to keep track of the number of elements.
B)Try different coefficients and subscripts to balance the number of atoms.
C)Begin with elements that appear only once on each side of the equation.
D)Change only the coefficients to balance the number of atoms.
12
The limiting reagent is the substance:
A)present in greatest quantity
B)limits the number of reagents present
C)determined by the amount of reactants present
D)that determines the maximum amount of possible product
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