Which of the following materials is most susceptible to chemical weathering by dissolution?

• A. Calcite (CaCO_3)
• B. Magnetite (Fe_3O_4)
• C. Quartz (SiO_2)
• D. Feldspar (KAlSi_3O_8)

Answer: (A)

Verified step by step guidance

1. Understand that chemical weathering by dissolution involves the breakdown of minerals when they react with water and acids, often leading to the mineral dissolving into ions.
2. Recall that minerals vary in their solubility and susceptibility to chemical weathering; minerals that are more soluble in acidic or neutral water will weather faster by dissolution.
3. Consider the chemical composition and structure of each mineral: Calcite (CaCO\_3) is a carbonate mineral that readily reacts with weak acids like carbonic acid in rainwater, leading to dissolution.
4. Compare this to Quartz (SiO\_2), which is very resistant to chemical weathering due to its strong silicon-oxygen bonds, and Magnetite (Fe\_3O\_4), which is an iron oxide and less soluble.
5. Feldspar (KAlSi\_3O\_8) weathers chemically but primarily through hydrolysis rather than direct dissolution, making Calcite the most susceptible to chemical weathering by dissolution among the options.