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.

22. A chemist claimed that the conversion of a metal oxide to a pure metal using H2 gas will always occur faster with a magnetic field than without a magnetic field. Do Figures 1-3 confirm this claim?

Answer and Explanation

Your Answer is

Correct Answer is J

Explanation

Look at figures 1 & 2 & 3. In the three figures, some dotted lines are on top, and some solid lines are on top, which means that some reactions are faster under the condition of magnetic field, and some are faster under the condition of no magnetic field. Fast, so the claim in the stem is wrong