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Chemistry, 7/e
Raymond Chang, Williams College
Mass Relationships in Chemical Reactions

Self Assessment B



1

Assume that magnesium consists of three isotopes having the abundances and masses given below. According to these data, calculate the average atomic mass of magnesium.
isotopeabundancemass
24;Mg78.70%23.985 amu
25Mg10.13%24.986 amu
26Mg11.17%25.983 amu
A)25.00 amu
B)2.431 amu
C)2431 amu
D)24.31 amu
E)None of the above.
2

One mole of H2
A)contains 6.0 x 1023 H atoms.
B)contains 6.0 x 1023 H2 molecules.
C)contains 1 g of H2.
D)is equivalent to 6.02 x 1023 g of H2.
E)None of the above.
3

How many oxygen atoms are present in 5.2 g of O2?
A)5.4 x 10-25 atoms
B)9.8 x 1022 atoms
C)2.0 x 1023 atoms
D)3.1 x 1024 atoms
E)6.3 x 1024 atoms
4

How many potassium atoms are present in 57.7 g of potassium hexafluoromanganate(IV), K2MnF6?
A)0.470 atoms
B)2.81 x 1023 atoms
C)0.233 atoms
D)1.41 x 1023 atoms
E)9.84 x 1023 atoms
5

What is the mass of 5.45 x 10-3 mol of glucose, C6 H12O6?
A)0.158 g
B)982 g
C)3.31 x 104 g
D)0.982 g
E)None of the above.
6

Determine the mass percent of iron in Fe4[Fe(CN)6] 3.
A)45% Fe
B)26% Fe
C)33% Fe
D)58% Fe
E)None of the above.
7

A compound composed of hydrogen and carbon contains 85.7% C and 14.3% H, and has a molar mass of 84 g/mol. What is the molecular formula of the compound?
A)CH2
B)C2H4
C)CH3
D)C3H6
E)C6H12
8

When it is correctly balanced, the correct coefficients for the equation below are PCl3 + H2O ----> H3PO3 + HCl
A)1, 3, 1, 1
B)1, 3, 1, 3
C)1, 1, 1, 3
D)2, 3, 2, 3
9

Hydrochloric acid can be prepared using the reaction described by the chemical equation: 2 NaCl(s) + H2SO4(l) ----> 2 HCl(g) + Na2 SO4(s). How many grams of HCl can be prepared from 393 g of H2SO4 and 4.00 moles of NaCl?
A)4.00 g
B)2.49 g
C)146 g
D)284 g
E)None of the above.
10

Calculate the percent yield of iron if 950 g of Fe3O4 underwent the reaction shown in the chemical equation below and 533 g of Fe was isolated from the reaction mixture. Fe3O4 (s) + 2 C(s) ----> 2 CO2 (g) + 3 Fe(s)
A)25.9%
B)77.5%
C)56.1%
D)None of the above.








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