Final answer:
The theoretical mass of sodium chloride (NaCl) produced from sodium carbonate (Na2CO3) is twice the mass of Na2CO3 because two moles of NaCl can be produced from one mole of Na2CO3, given the stoichiometry of the reaction.
Step-by-step explanation:
To calculate the theoretical mass of sodium chloride residue from an unknown carbonate sample, we should consider the stoichiometry of the reaction involved. If sodium carbonate (Na2CO3) reacts to form sodium chloride (NaCl), the mass of NaCl formed depends on the proportion of sodium carbonate reacting. Given that the chemical formula for NaCl includes one atom of sodium and one atom of chlorine, we use the molar mass of NaCl to determine the theoretical mass from the available Na2CO3.
First, the molar mass of NaCl is calculated by adding the atomic masses of sodium (22.99 amu) and chlorine (35.45 amu), for a total of 58.44 amu or g/mol. Now, if the mass of Na2CO3 is taken as a basis for the reaction, we can predict that, since there are two sodium atoms for every molecule of Na2CO3, two moles of NaCl can be produced from one mole of Na2CO3. Therefore, the theoretical mass of sodium chloride would be twice the mass of Na2CO3.
In the case of our unknown sample, if we assume that it is Na2CO3, and we do not know the actual mass, the theoretical mass of NaCl will correspond to twice the mass of the Na2CO3 present. So the answer to the question would be 2 × the mass of Na2CO3.