Answer:
BaSO₄ has 4 oxygens. Ba(OH)₂ has 2 oxygens.
Explanation:
The number of any one element is the coefficient times the subscript of that element. In BaSO₄, the coefficient is 1 and the subscript for oxygen is 4. In Ba(OH)₂, the coefficient is 1 and the subscript is 2. In Ba(OH)₂, the subscript is outside the () because OH⁻ is an ion and the subscript applies to both elements in the ().
