A cell is the smallest unit of life, also called the 'building blocks of life' because cells multiply and differentiate to form a multicellular organism as well as give rise to new organism by forming gametes or reproductive spores. A living thing, whether made of one cell (like bacteria) or many cells (like a human), is called an organism. Thus, cells are the basic building blocks of all organisms. Several systems that function together form an organism (like a human being).
In a) the final equation is AgNO3 + KCl = AgCl + KNO3, b) Ni(NO3)2 + Na2S = 2NaNO3 + NiS; c) CaCl2 + Na2CO3 = 2 NaCl + CaCO3. In 2) The total net equation is Ca 2+ + CO32- = CaCO3 (s).