The agent of chemical weathering that produces weak acids to dissolve rock is carbon dioxide (CO2). Here's how it works:

* CO2 in the atmosphere: CO2 is naturally present in the atmosphere.

* CO2 dissolves in water: Rainwater absorbs CO2 from the atmosphere, forming carbonic acid (H2CO3). This is a weak acid, but it's still acidic enough to react with certain minerals.

* Dissolving rocks: Carbonic acid reacts with minerals like calcite (found in limestone and marble) to form calcium bicarbonate, which is soluble in water. This process is called carbonation.

* Chemical weathering: This chemical reaction weakens the rock, causing it to break down over time.

Example: Think of a limestone cave. The formation of these caves is due to the chemical weathering process of carbonation. The weak carbonic acid in rainwater dissolves the limestone over thousands of years, creating the characteristic cave formations.

Let me know if you'd like to know more about other agents of chemical weathering!