Which of the following is an unbalanced equation? CS_(2)+underline (2)O_(2)-gt CO_(2)+underline (2)SO_(2) underline (2)Na+underline (2)H_(2)O-gt underline (2)NaOH+H_(2) PbO_(2)+underline (2)H_(2)-gt underline (2)Pb+H_(2)O CaCO_(3)... CaO+CO_(2)

The correct answer is: $CaCO_{3}\cdots CaO+CO_{2}$<br /><br />Explanation: An unbalanced chemical equation is one in which the number of atoms of each element is not the same on both sides of the equation. In the given options, the equation $CaCO_{3}\cdots CaO+CO_{2}$ is unbalanced because the number of atoms of each element is not the same on both sides.