During a chemical reaction, mass and energy are both conserved.
Answer: D
Explanation
A chemical reaction occurs following law of conservation of mass and law of constant proportion.
So according to law of mass conservation, the sum of the reactants' mass should be same with the sum of the products' mass. So, the chemical reaction conserved the mass.
And according to thermodynamics, a chemical reaction will be balanced or will be in equilibrium when the Gibbs free energy change (ΔG) is zero.
The Gibbs free energy change is the difference of the energies between the reactants and product sides.
So according to this, the energy is also conserved during a balanced chemical reaction.
Thus the law of mass conservation and the zero Gibbs' free energy change confirms that both the mass and energy should be conserved for a balanced chemical reaction.