2HCl + Ca(OH)2 = CaCl2 + 2H20
Before balancing on the left side there was 1 chlorine (Cl) atom, 2 oxygen (O) atom, 2 hydrogens (H) atoms and 1 calcium (Ca) atom. In the right side, there was 2 chlorine (Cl) atoms, 1 oxygen (O) atom, 2 hydrogens (H) atoms and 1 calcium (Ca) atom.
To balance the chemical equation we hat to place a coefficient of 2 in front of HCl, and coefficient 2 of in front of H2O.