Question

When a clear aqueous solution of calcium chloride (CaCl2) is mixed with a clear aqueous solution of sodium carbonate (Na2CO3), a white solid precipitate forms. What happens to the mass of the mixture after the solid precipitate forms? Choose the best answer.
Mass decreases because the chemical reaction results in a loss of mass.
Mass increases because solid precipitate weighs more than liquid.
Mass increases because the density of the solution increases.
No change because the number of atoms remains the same.
Mass decreases because the starting reactants are used up.

Answer 1

Na2CO3 + CaCl2 ==> CaCO3 + 2NaCl

The Law of conservation of mass says that the mass on the left = mass on the right.

Answer 2

No change because the number of atoms remains the same