Answer: The coefficient that should be placed in front of NaCl to balance this equation is 2.
Explanation: The balanced equation for the reaction between BaCl2(aq) and Na2CO3(aq) is :
BaCl2(aq) + Na2CO3(aq) --> BaCO3(s) + 2NaCl(aq)
In the unbalanced equation given, there is 1 mole of NaCl produced from 1 mole of BaCl2(aq) and 1 mole of Na2CO3(aq). But according to the balanced equation, 2 moles of NaCl is produced. Therefore, to balance the equation, a coefficient of 2 should be placed in front of NaCl.
The balanced equation will be: BaCl2(aq) + Na2CO3(aq) --> BaCO3(s) + 2NaCl(aq)