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.
No change because the number of atoms remains the same
Na2CO3 + CaCl2 ==> CaCO3 + 2NaCl
The Law of conservation of mass says that the mass on the left = mass on the right.
The correct answer is: Mass increases because the solid precipitate weighs more than the liquid.
To determine what happens to the mass of the mixture after the solid precipitate forms, we need to consider the law of conservation of mass. According to this law, mass is neither created nor destroyed in a chemical reaction. The total mass of the reactants before the reaction should be equal to the total mass of the products after the reaction.
In this case, when a clear aqueous solution of calcium chloride (CaCl2) and a clear aqueous solution of sodium carbonate (Na2CO3) are mixed, a chemical reaction occurs, resulting in the formation of a white solid precipitate.
The balanced chemical equation for this reaction is:
CaCl2(aq) + Na2CO3(aq) → CaCO3(s) + 2NaCl(aq)
From the equation, we can see that the reaction leads to the formation of a solid precipitate (CaCO3) and a soluble salt (NaCl) in aqueous solution. Since the mass of the precipitate is derived from the reactants, the mass of the mixture after the solid precipitate forms does not change. Therefore, the correct answer is:
No change because the number of atoms remains the same.