[ريم علي الشهري]

Chapter 3 Mass Relationships in Chemical Reactions


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1. What is the mass, in grams, of one copper atom ?
A.​ 1.055 ´ 10-22 g
B.​63.55 g
C.​1 amu
D.​1.66 ´ 10-24 g
E.​9.476 ´ 1021 g


2.​Determine the number of moles of aluminum in 96.7 g of Al.
A. 0.279 mol
B.​3.58 mol
C.​7.43 mol
D.​4.21 mol
E.​6.02 ´ 1023 mol


3.​Which of the following samples contains the greatest number of atoms ?
A. 100 g of Pb
B.​2.0 mole of Ar
C.​0.1 mole of Fe
D.​5 g of He
E.​20 million O2 molecules


4.​Formaldehyde has the formula CH2O. How many molecules are there in 0.11 g of formaldehyde ?
A. 6.1 ´ 10-27
B.​3.7 ´ 10-3
C.​4
D.​2.2 ´ 1021
E.​6.6 ´ 1022


5.​How many sulfur atoms are present in 25.6 g of Al2(S2O3)3 ?
A.​ 0.393
B.​6
C.​3.95 ´ 1022
D.​7.90 ´ 1022
E.​2.37 ´ 1023


6.​The percent composition by mass of a compound is 76.0% C, 12.8% H, and 11.2% O. The molar mass of this compound is 284.5 g/mol. What is the molecular formula of the compound ?
A. C10H6O
B.​C9H18O
C.​C16H28O4
D.​C20H12O2
E.​C18H36O2


7.​What is the coefficient of H2O when the following equation is properly balanced with the smallest set of whole numbers ?
___ Al4C3 + ___ H2O ® ___ Al(OH)3 + ___ CH4
A. 3
B.​4
C.​6
D.​12
E.​24


8.​When 22.0 g NaCl and 21.0 g H2SO4 are mixed and react according to the equation below, which is the limiting reagent ?
2NaCl + H2SO4 ® Na2SO4 + 2HCl
A. NaCl
B.​H2SO4
C.​Na2SO4
D.​HCl
E.​No reagent is limiting.

9.​How many grams of Cl2 can be prepared from the reaction of 16.0 g of MnO2 and 30.0 g of HCl according to the following chemical equation ?
MnO2 + 4HCl ® MnCl2 + Cl2 + 2H2O
A. 0.82 g
B.​5.8 g
C.​13.0 g
D.​14.6 g
E.​58.4 g


10.​What is the theoretical yield of chromium that can be produced by the reaction of 40.0 g of Cr2O3 with 8.00 g of aluminum according to the chemical equation below ?
2Al + Cr2O3 ® Al2O3 + 2Cr
A. 7.7 g
B.​15.4 g
C.​27.3 g
D.​30.8 g
E.​49.9 g

Answer Key


1.A

2.B

3.B

4.D

5.E

6.E

7.D

8.A

9.C

10.B