Passage IV
If a metal oxide sample at high temperature is exposed to a stream of H2 gas, it may be converted to a pure metal. Reactions 1-3 are examples of this process for a cobalt oxide and 2 different iron oxides, respectively.
Reaction 1: CoO + H2 → Co + H2O
Reaction 2: FeO + H2 → Fe + H2O
Reaction 3: Fe3O4 + 4H2 → 3Fe + 4H2O
During the reaction, the H2 stream carries away H2O, so the resulting sample is composed of metal oxide and pure metal only.
Figures 1-3 show how the percent of pure metal, ％ PM, in metal oxide samples changed over time as they underwent Reactions 1-3, respectively, with and without a magnetic field present.
％ PM =
Figure 1 adapted from M. W. Rowe et al., "Effect of Magnetic Field on Reduction of Cobalt Oxides." @1979 by Chapman and Hall Ltd.
Figures 2 and 3 adapted from M. W. Rowe, S. M. Lake, and R. Fanick, "Effect of Magnetic Field on Reduction of Iron Oxides: Magnetite and Wüstite." @1977 by Macmillan Magazines Ltd.
19. According to Figure 2, during Reaction 2 without a magnetic field, the % PM at 10 min was approximately:
Your Answer is
Correct Answer is C
Explanation
Look at the dotted line in figure 2 (without magnetic field), when the abscissa time is 10 min, the ordinate %MP is 45