Question

heartburn occurs when stomach acid escapes the stomach and burns the tissues of the esophagus. baking soda is sometimes used as an antacid. how does baking soda help relieve symptoms of heartburn? multiple choice the baking soda increases the acidity of the stomach. the baking soda releases salt which draws more water into the esophagus thereby diluting the acid. the baking soda relaxes the stomach muscles. the baking soda is serving as a buffer to remove excess h⁺ ions from stomach acid. the baking soda is able to coat the lining of the esophagus thereby protecting it from the acid.

Explanation:

1. Analyze Option 1: Increasing stomach acidity would worsen heartburn, so this is incorrect.
2. Analyze Option 2: Baking soda (sodium bicarbonate) does not act by releasing salt to draw water for dilution in this context; this mechanism is incorrect.
3. Analyze Option 3: Baking soda does not relax stomach muscles; muscle relaxation is not its mode of action for heartburn relief.
4. Analyze Option 4: Baking soda ($\text{NaHCO}_3$) is a base - buffer. Stomach acid is acidic (has excess $\text{H}^+$ ions). The bicarbonate ion ($\text{HCO}_3^-$) in baking soda can react with $\text{H}^+$ ions (from stomach acid: $\text{HCO}_3^-+\text{H}^+

ightleftharpoons\text{H}_2\text{CO}_3$) to reduce the concentration of free $\text{H}^+$ ions, thus acting as a buffer to neutralize excess acid. This is the correct mechanism.

1. Analyze Option 5: Baking soda does not coat the esophagus lining to protect it; its main action is related to acid - base chemistry, not physical coating for this purpose.

Answer:

The baking soda is serving as a buffer to remove excess $\text{H}^+$ ions from stomach acid.