If MgCO₃ undergoes a double replacement reaction in 6 M HCl, and one of the resulting products then undergoes a decomposition reaction, the gas that evolves is:

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11ecba2d_11eb_2322_a3bf_ab25cffd55c5_MD0008_00 Double replacement reactions involve an exchange of constituent bonding partners between two reacting compounds and result in the formation of two new product compounds. For double replacement reactions between two ionic species, the cations and anions of the two compounds exchange counter ions. Decomposition reactions follow the pattern of one reactant species breaking down (decomposing) into two or more product species. Applying bonding patterns for recognized reaction types allows the prediction of reaction products. If MgCO₃ undergoes a double replacement reaction in 6 M HCl, the Mg⁺² and CO₃⁻² ions in MgCO₃ exchange bonding partners with the H⁺ and Cl⁻ ions in HCl (cations pairing with anions). This causes the formation of water-soluble MgCl₂ (an ionic salt) and H₂CO₃ (an unstable acid). The unstable H₂CO₃ undergoes a decomposition reaction and breaks down (decomposes) into H₂O and CO₂ (carbon dioxide), which then evolves from the solution. (Choice A) The H⁺ ions in solution have lower electronegativity than the oxygen atoms and cannot retain the electrons necessary to form the H-H bond present in hydrogen gas (H₂). (Choice C) As seen in the Lewis structure of carbonic acid (H₂CO₃), the oxygen atoms are separately bonded to the carbon atom and cannot readily associate to form oxygen gas (O₂). Instead, an acidic proton (H⁺) is easily transferred in solution between the two hydroxyl groups to form a good leaving group (a water molecule), which facilitates the breakdown of the molecule. (Choice D) MgO is a water-soluble, ionic solid that does not form in the described double replacement reaction. The CO₃⁻² anion does not fragment into O⁻² anions that could bind with Mg⁺² ions. Educational objective: Double replacement reactions involve the exchange of the bonding partners of two reactant compounds, forming two new product compounds. Decomposition reactions involve a single compound breaking down into two or more new compounds. Understanding reaction types and bonding patterns allows the prediction of reaction products.

If MgCO3 Undergoes a Double Replacement Reaction in 6 M

If MgCO₃ Undergoes a Double Replacement Reaction in 6 M