Why does one take Pepto-Bismol or milk of magnesia for an upset stomach?

Question

Explain what happens in the body.

Answer 1

Magnesium hydroxide is an antacid that can help with upset stomach associated with hyperacidity (aka acid/gastric reflux). it works to neutralize HCl (hydrochloric acid) produced by your stomach.

 

This is a classic neutralization reaction with a strong acid and strong base.

2HCl(aq) + Mg(OH)2(s) → MgCl2(aq) + 2H2O(l)

 

Answer 2

Hint: Pepto-Bismol and milk of magnesia (aka magnesium hydroxide) are antacids.