Problem 95 - Chemistry: The Central Science

Question

Antacids are often used to relieve pain and promote healing in the treatment of mild ulcers. Write balanced net ionic equations for the reactions between the aqueous \(\mathrm{HCl}\) in the stomach and each of the following substances used in various antacids: (a) \(\mathrm{Al}(\mathrm{OH})_{3}(s)\), (b) \(\mathrm{Mg}(\mathrm{OH})_{2}(s)\), (c) \(\mathrm{MgCO}_{3}(s)\), (d) \(\mathrm{NaAl}\left(\mathrm{CO}_{3}\right)(\mathrm{OH})_{2}(s),(e) \mathrm{CaCO}_{3}(s)\).

Step-by-Step Solution

Answer

(a) \[\mathrm{Al}(\mathrm{OH})_{3}(s) + 3\mathrm{H^{+}(aq)} \rightarrow \mathrm{Al^{3+}(aq)} + 3\mathrm{H}_{2}\mathrm{O}(l)\] (b) \[\mathrm{Mg}(\mathrm{OH})_{2}(s) + 2\mathrm{H^{+}(aq)} \rightarrow \mathrm{Mg^{2+}(aq)} + 2\mathrm{H}_{2}\mathrm{O}(l)\] (c) \[\mathrm{MgCO}_{3}(s) + 2\mathrm{H^{+}(aq)} \rightarrow \mathrm{Mg^{2+}(aq)} + \mathrm{H}_{2}\mathrm{O}(l) + \mathrm{CO}_{2}(g)\] (d) \[\mathrm{NaAl}\left(\mathrm{CO}_{3}\right)(\mathrm{OH})_{2}(s) + 6\mathrm{H^{+}(aq)} \rightarrow \mathrm{Al^{3+}(aq)}+ 2\mathrm{Na^{+}(aq)} + 5\mathrm{H}_{2}\mathrm{O}(l) + \mathrm{CO}_{2}(g)\] (e) \[\mathrm{CaCO}_{3}(s) + 2\mathrm{H^{+}(aq)} \rightarrow \mathrm{Ca^{2+}(aq)} + \mathrm{H}_{2}\mathrm{O}(l) + \mathrm{CO}_{2}(g)\]

Step 1: (a) Reaction with \(\mathrm{Al}(\mathrm{OH})_{3}(s)\)

Step 1: Write the balanced chemical equation \[\mathrm{Al}(\mathrm{OH})_{3}(s) + 3\mathrm{HCl(aq)} \rightarrow \mathrm{AlCl}_3(aq) + 3\mathrm{H}_{2}\mathrm{O}(l)\] Step 2: Break the strong electrolytes into their constituent ions \[\mathrm{Al}(\mathrm{OH})_{3}(s) + 3\mathrm{H^{+}(aq)} + 3\mathrm{Cl^{-}(aq)} \rightarrow \mathrm{Al^{3+}(aq)} + 3\mathrm{Cl^{-}(aq)} + 3\mathrm{H}_{2}\mathrm{O}(l)\] Step 3: Cancel out the spectator ions The net ionic equation is: \[\mathrm{Al}(\mathrm{OH})_{3}(s) + 3\mathrm{H^{+}(aq)} \rightarrow \mathrm{Al^{3+}(aq)} + 3\mathrm{H}_{2}\mathrm{O}(l)\]

Step 2: (b) Reaction with \(\mathrm{Mg}(\mathrm{OH})_{2}(s)\)

Step 1: Write the balanced chemical equation \[\mathrm{Mg}(\mathrm{OH})_{2}(s) + 2\mathrm{HCl(aq)} \rightarrow \mathrm{MgCl}_2(aq) + 2\mathrm{H}_{2}\mathrm{O}(l)\] Step 2: Break the strong electrolytes into their constituent ions \[\mathrm{Mg}(\mathrm{OH})_{2}(s) + 2\mathrm{H^{+}(aq)} + 2\mathrm{Cl^{-}(aq)} \rightarrow \mathrm{Mg^{2+}(aq)} + 2\mathrm{Cl^{-}(aq)} + 2\mathrm{H}_{2}\mathrm{O}(l)\] Step 3: Cancel out the spectator ions The net ionic equation is: \[\mathrm{Mg}(\mathrm{OH})_{2}(s) + 2\mathrm{H^{+}(aq)} \rightarrow \mathrm{Mg^{2+}(aq)} + 2\mathrm{H}_{2}\mathrm{O}(l)\]

Step 3: (c) Reaction with \(\mathrm{MgCO}_{3}(s)\)

Step 1: Write the balanced chemical equation \[\mathrm{MgCO}_{3}(s) + 2\mathrm{HCl(aq)} \rightarrow \mathrm{MgCl}_{2}(aq) + \mathrm{H}_{2}\mathrm{O}(l) + \mathrm{CO}_{2}(g)\] Step 2: Break the strong electrolytes into their constituent ions \[\mathrm{MgCO}_{3}(s) + 2\mathrm{H^{+}(aq)} + 2\mathrm{Cl^{-}(aq)} \rightarrow \mathrm{Mg^{2+}(aq)} + 2\mathrm{Cl^{-}(aq)} + \mathrm{H}_{2}\mathrm{O}(l) + \mathrm{CO}_{2}(g)\] Step 3: Cancel out the spectator ions The net ionic equation is: \[\mathrm{MgCO}_{3}(s) + 2\mathrm{H^{+}(aq)} \rightarrow \mathrm{Mg^{2+}(aq)} + \mathrm{H}_{2}\mathrm{O}(l) + \mathrm{CO}_{2}(g)\]

Step 4: (d) Reaction with \(\mathrm{NaAl}\left(\mathrm{CO}_{3}\right)(\mathrm{OH})_{2}(s)\)

Step 1: Write the balanced chemical equation \[\mathrm{NaAl}\left(\mathrm{CO}_{3}\right)(\mathrm{OH})_{2}(s) + 6\mathrm{HCl(aq)} \rightarrow \mathrm{AlCl}_3(aq) + 2 \mathrm{NaCl(aq)}+ 5\mathrm{H}_{2}\mathrm{O}(l) + \mathrm{CO}_{2}(g)\] Step 2: Break the strong electrolytes into their constituent ions \[\mathrm{NaAl}\left(\mathrm{CO}_{3}\right)(\mathrm{OH})_{2}(s) + 6\mathrm{H^{+}(aq)} + 6\mathrm{Cl^{-}(aq)} \rightarrow \mathrm{Al^{3+}(aq)} + 3\mathrm{Cl^{-}(aq)}+ 2\mathrm{Na^{+}(aq)} + 2\mathrm{Cl^{-}(aq)} + 5\mathrm{H}_{2}\mathrm{O}(l) + \mathrm{CO}_{2}(g)\] Step 3: Cancel out the spectator ions The net ionic equation is: \[\mathrm{NaAl}\left(\mathrm{CO}_{3}\right)(\mathrm{OH})_{2}(s) + 6\mathrm{H^{+}(aq)} \rightarrow \mathrm{Al^{3+}(aq)}+ 2\mathrm{Na^{+}(aq)} + 5\mathrm{H}_{2}\mathrm{O}(l) + \mathrm{CO}_{2}(g)\]

Step 5: (e) Reaction with \(\mathrm{CaCO}_{3}(s)\)

Step 1: Write the balanced chemical equation \[\mathrm{CaCO}_{3}(s) + 2\mathrm{HCl(aq)} \rightarrow \mathrm{CaCl}_{2}(aq) + \mathrm{H}_{2}\mathrm{O}(l) + \mathrm{CO}_{2}(g)\] Step 2: Break the strong electrolytes into their constituent ions \[\mathrm{CaCO}_{3}(s) + 2\mathrm{H^{+}(aq)} + 2\mathrm{Cl^{-}(aq)} \rightarrow \mathrm{Ca^{2+}(aq)} + 2\mathrm{Cl^{-}(aq)} + \mathrm{H}_{2}\mathrm{O}(l) + \mathrm{CO}_{2}(g)\] Step 3: Cancel out the spectator ions The net ionic equation is: \[\mathrm{CaCO}_{3}(s) + 2\mathrm{H^{+}(aq)} \rightarrow \mathrm{Ca^{2+}(aq)} + \mathrm{H}_{2}\mathrm{O}(l) + \mathrm{CO}_{2}(g)\]

Key Concepts

Acid-Base Reactions

Acid-base reactions are a fundamental concept in chemistry. These reactions occur when an acid and a base interact. In these reactions, the acid donates protons (H⁺ ions) to the base. As a result, water and various salts are often produced.
An essential part of this process is the neutralization of acidic and basic substances. When a strong acid, like hydrochloric acid (HCl), comes into contact with a substance like aluminum hydroxide (Al(OH)₃), we see a typical acid-base reaction.
During the reaction, the base (Al(OH)₃) neutralizes the acid (HCl), which helps in decreasing the acidity of the solution. Such reactions are essential for understanding how antacids work to reduce stomach acid.

Antacid Reactivity

Antacids are substances used to neutralize stomach acid and relieve indigestion. They often contain bases like calcium carbonate or magnesium hydroxide. When these bases react with the hydrochloric acid in your stomach, they form salts and water.
For example, magnesium hydroxide (Mg(OH)₂) reacts with hydrochloric acid to form magnesium chloride and water, thereby reducing the acidity in the stomach.
This proactive chemistry is why antacids are effective at treating heartburn and providing relief from acid-related conditions. Understanding the reactivity of antacids helps in determining their effectiveness based on the elements they contain.

Chemical Reactions

Chemical reactions involve the transformation of substances through the breaking and forming of chemical bonds. They are fundamental to understanding chemical properties and changes.
Each chemical reaction, such as the one between magnesium carbonate (MgCO₃) and hydrochloric acid, demonstrates how reactants transform into products. Magnesium carbonate reacts with HCl, releasing carbon dioxide gas, water, and magnesium chloride.
Identifying the products makes it easier to predict the outcome of the reaction and its impact, such as reduced acidity in the case of antacids.

Chemical Equation Balancing

Balancing chemical equations is a crucial skill in chemistry. This process ensures that the same number of each type of atom appears on both sides of the equation.
For instance, during the reaction of calcium carbonate (CaCO₃) with hydrochloric acid, balancing involves making sure that the quantities of calcium, carbon, oxygen, hydrogen, and chlorine are equal on both sides.
Balancing these equations ensures that your calculations and predictions about the reaction are accurate. It provides visualization of how reactants are converted into products, leaving no discrepancies in mass and atom count.