Question

1. chalk is mainly composed of: caco₃ na₂co₃ k₂co₃ mgco₃ 49. the formula of water is: ho h₂o h₂o₂ o₂h

Explanation:

Chalk is mainly calcium carbonate ($CaCO_3$). Water is composed of two hydrogen atoms and one oxygen atom, with the chemical formula $H_2O$.

Answer:

1. $CaCO_3$
2. $H_2O$