Passage
The alkaline-earth metals are a highly reactive family of metals occupying Group 2 (IIA) of the periodic table. In their elemental form, the alkaline-earth metals have a shiny, silvery-white to slightly yellowish appearance. The alkaline-earth metals exhibit some similarities to the chemistry of the alkali metals (Group 1) but are a little less reactive.Atoms of the alkaline-earth metals (M) have only two valence electrons and a low first and second ionization energy. Consequently, these metals readily lose both electrons to produce cations with a +2 charge (M⁺²) during reactions with nonmetals. As a result, the alkaline-earth metals do not exist in their elemental metallic form in nature. Instead, the Group 2 elements are found primarily as metal oxides, which form by reacting oxygen (Reaction 1) .

Similarly, elemental samples of alkaline-earth metals will react with elemental halogens (X₂) to form metal halides (Reaction 2) , all of which are ionic except for BeCl₂.

Except for beryllium, the alkaline-earth metals react with water to produce very basic metal hydroxide solutions and hydrogen gas (Reaction 3) .

The most difficult alkaline-earth metal to study is radium, because it is a rare radioactive element that is produced from the nuclear decay of uranium. The most common natural isotope, radium-226, has a half-life of 1,600 years and decays by alpha emission into radon-222 (Reaction 4) .

-Based on the reaction in Figure 1 and the energy profile in Figure 2, which statement correctly describes both Compound 2 and Compound 3?

Question

Passage
The alkaline-earth metals are a highly reactive family of metals occupying Group 2 (IIA) of the periodic table. In their elemental form, the alkaline-earth metals have a shiny, silvery-white to slightly yellowish appearance. The alkaline-earth metals exhibit some similarities to the chemistry of the alkali metals (Group 1) but are a little less reactive.Atoms of the alkaline-earth metals (M) have only two valence electrons and a low first and second ionization energy. Consequently, these metals readily lose both electrons to produce cations with a +2 charge (M⁺²) during reactions with nonmetals. As a result, the alkaline-earth metals do not exist in their elemental metallic form in nature. Instead, the Group 2 elements are found primarily as metal oxides, which form by reacting oxygen (Reaction 1) .

Similarly, elemental samples of alkaline-earth metals will react with elemental halogens (X₂) to form metal halides (Reaction 2) , all of which are ionic except for BeCl₂.

Except for beryllium, the alkaline-earth metals react with water to produce very basic metal hydroxide solutions and hydrogen gas (Reaction 3) .

The most difficult alkaline-earth metal to study is radium, because it is a rare radioactive element that is produced from the nuclear decay of uranium. The most common natural isotope, radium-226, has a half-life of 1,600 years and decays by alpha emission into radon-222 (Reaction 4) .

-Based on the reaction in Figure 1 and the energy profile in Figure 2, which statement correctly describes both Compound 2 and Compound 3?

Quizplus · Accepted Answer

11ecba2d_11e9_274d_a3bf_f96bd57fede9_MD0008_00 When a reaction can produce more than one product, how much of each product is formed often depends on thermodynamic and kinetic considerations. During product formation, the compound with the lowest energy transition state (lowest energy barrier for formation) forms fastest, making it the kinetic product. The compound with the most stable (lowest energy) structure is the thermodynamic product, but because it has a higher energy transition state (higher energy barrier for formation), it forms more slowly. Because the kinetic product has a lower energy barrier for formation, at lower temperatures the kinetic product will be the major product produced. In such a case, the reaction is said to be under kinetic control. However, at higher temperatures the additional energy enables the reaction to overcome the larger energy barrier for the formation of the thermodynamic product, making it the major product formed. In this alternate case, the reaction is said to be under thermodynamic control. For the reaction to form Compounds 2 and 3, the energy diagram of the reaction shows that Compound 2 has a lower energy transition state than Compound 3. Therefore, Compound 2 will form faster and is the kinetic product. Compound 3 has a higher energy transition state, but it is more stable (lower energy) than Compound 2. Therefore, Compound 3 is the thermodynamic product. (Choice A) Compounds 2 and 3 have transition states of different energies and form at different rates. Both cannot be the kinetic product. (Choice C) Compound 2 forms faster and is higher in energy than Compound 3. Therefore, Compound 2 is the kinetic product, not Compound 3. (Choice D) Compounds 2 and 3 are not equally stable (they have different energies). Both cannot be the thermodynamic product. Educational objective: For a reaction producing more than one product, the product with the lowest energy transition state will form fastest and is the kinetic product. The compound with a higher energy transition state that produces the lowest energy (most stable) structure is the thermodynamic product.