Answer:
19. because fire needs oxygen or air to keep the fire burning.
20.A molecule of sodium chloride, NaCl, consists of one atom each of sodium and chlorine. Hence, each molecule of NaCl has 2 atoms total. Similarly, we can calculate the total number of atoms in 1 mole of sodium chloride. Since 1 molecule contains 1 atom each of Na and Cl, 1 mole of NaCl will contain 1 mole each of Na and Cl.
Step-by-step explanation:
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