Question

can combine with water to form carbonic acid. then, h₂co₃ falls as rain to earth’s surface. sometimes it falls directly into the ocean, but this weak acid can also enter the soils and cracks in rocks on land. it reacts with minerals in rocks that contain little carbon, like granite and basalt, and breaks them down in a multistep process called chemical weathering. these chemical reactions release ions, such as calcium ions (ca²⁺) and bicarbonate ions (hco₃⁻), which are carried into the oceans by rivers and runoff. this process prevents carbon in rainwater from immediately returning to the atmosphere.
over time, acidic rainwater slowly weathers rocks like granite into clays.
limestone is mostly made of sediment and the fossilized remains of ancient marine organisms.
marine organisms like clams and corals combine co₃²⁻ ions with ca²⁺ ions from weathered rocks to form calcium carbonate (caco₃), which makes up their shells and exoskeletons. when these organisms die, their mineralized parts sink to the ocean floor and become fossilized. over time, fossilized shells and exoskeletons mix with sediment to form carbon - rich rock in a process called limestone formation. carbon can be stored in limestone for millions of years!
match each term to its description.
chemical weathering
gas exchange
limestone formation
during this process, rocks on land are broken down by carbonic acid, forming various ions. carbon is removed from the atmosphere.
during this process, the fossilized remains of marine organisms mix with sediment to produce a type of carbon - rich rock.
during this process, carbon dioxide dissolves into ocean water and forms carbonic acid, which breaks down into simple ions. this process can also happen in reverse.

Explanation:

1. For the first description ("During this process, rocks on land are broken down by carbonic acid, forming various ions. Carbon is removed from the atmosphere."): From the text, chemical weathering is the process where acidic rainwater (carbonic acid) reacts with minerals in rocks (like granite, basalt) on land, breaks them down, and releases ions. So this matches "chemical weathering".
2. For the second description ("During this process, the fossilized remains of marine organisms mix with sediment to produce a type of carbon - rich rock."): The text says that when marine organisms die, their fossilized parts mix with sediment to form limestone in the limestone formation process. So this matches "limestone formation".
3. For the third description ("During this process, carbon dioxide dissolves into ocean water and forms carbonic acid, which breaks down into simple ions. This process can also happen in reverse."): Gas exchange (related to the carbon cycle here) involves CO₂ dissolving in ocean water to form carbonic acid (and can reverse, like when CO₂ is released back). So this matches "gas exchange".

Answer:

1. "During this process, rocks on land are broken down by carbonic acid, forming various ions. Carbon is removed from the atmosphere." - chemical weathering
2. "During this process, the fossilized remains of marine organisms mix with sediment to produce a type of carbon - rich rock." - limestone formation
3. "During this process, carbon dioxide dissolves into ocean water and forms carbonic acid, which breaks down into simple ions. This process can also happen in reverse." - gas exchange