Question 69: Which of the following statements are NOT correct?
A. Hydrogen is used to reduce heavy metal oxides to metals.
B. Heavy water is used to study reaction mechanism.
C. Hydrogen is used to make saturated fats from oils.
D. The \mathrm{H}-\mathrm{H} bond dissociation enthalpy is lowest as compared to a single bond between two atoms of any element.
E. Hydrogen reduces oxides of metals that are more active than iron.
Choose the most appropriate answer from the options given below :
(1) D, E only
(2) A, B, C only
(3) B, C, D, E only
(4) B, D only
Answer: Option (1)
Explanation:
Hydrogen is commonly used as a reducing agent for heavy metal oxides such as copper oxide,
so statement A is correct.
Heavy water \mathrm{D_2O} is used as an isotopic tracer to study reaction mechanisms,
so statement B is correct.
Hydrogen is used in the hydrogenation of vegetable oils to form saturated fats,
making statement C correct.
The \mathrm{H\!-\!H} bond dissociation enthalpy is very high
and not the lowest among single bonds, so statement D is incorrect.
Hydrogen cannot reduce oxides of metals that are more active than iron,
so statement E is incorrect.
Therefore, the statements that are NOT correct are D and E,
corresponding to option (1).