Final answer:
The coefficient required in front of CaCl2 to balance calcium when a coefficient of 3 is in front of CaSO4 is 3. This ensures that the atoms of calcium are balanced on both sides of the equation.
Step-by-step explanation:
When balancing chemical equations, it is important to ensure that the number of atoms of each element is the same on both sides of the equation. If we have placed a coefficient of 3 in front of CaSO4, this provides us with 3 calcium (Ca) atoms. In order to balance the calcium atoms on the other side of the equation, we need the same number of calcium atoms. As the chemical formula for calcium chloride is CaCl2, which contains one calcium atom per formula unit, the coefficient needed in front of CaCl2 to balance calcium (Ca) is also 3. Therefore, the answer is b) 3.