Which substance is a common weak base found in many household products?

Ammonia (NH3) is indeed a common weak base found in many household products. It typically exists in household cleaning agents due to its ability to break down grime and its effectiveness in removing odors. As a weak base, ammonia does not completely ionize in solution, which results in a less aggressive reaction compared to strong bases. This property makes it a safer option for many cleaning applications where a more potent base could cause damage to surfaces or pose safety risks.

Additionally, ammonia's ability to act as a weak base is highlighted by its reaction with acids to form ammonium salts, showcasing its buffering capability. This characteristic is desirable in household cleaners, as it allows for effective cleaning without the harshness of stronger bases.

In contrast, the other options listed are all strong bases or are not categorized as common household weak bases. Sodium hydroxide (NaOH) and calcium hydroxide (Ca(OH)2) are strong bases that can be corrosive and are typically used in heavier-duty cleaning tasks rather than general household cleaning. Bicarbonate (HCO3-) can act as a weak base but is not as commonly recognized for its use in discrete household cleaning products as ammonia is.