Hcl is slowly added to aqueous na2co3 forming nacl, h2o, and co2. follow the steps above to write a balanced equation for this reaction .

 The  balanced  equation is as  below

Na2CO3 +2 HCl → 2 NaCl  +H2O  + CO2

Explanation

 step 1 : write  the unbalanced chemical  equation

that is  Na2CO3  +  HCl→  NaCl  + H2O  +CO2

Step 2: change  the coefficient ( number in front  of chemical  formula)  to make  sure  the  number of  atoms  of  an  element  are the same in both side.

By adding 2 in front  of HCl  and  in front  of NaCl  balance the    equation.

Therefore the balanced equation is as  below

Na2CO3  +2HCl  → 2NaCl  +H2O +Co2

answer : one can design an experiment using a liquid and an additive that can be added to the liquid and observe the chemical changes in the reaction species.

one would need a beaker which is filled with a known amount of the liquid in which thermometer is placed to measure the temperature changes; after addition of the additive to the liquid solution one can note down the temperature change and find whether the reaction is endothermic or exothermic in nature. by subtracting the initial temperature value with the final temperature one can find the temperature changes.

various combinations of liquid and additive can be used. liquid in this case can be a known quantity of water and additives can be epsom salt or without epsom salt the experiment can be conducted to notice the changes. water and ice, hydrogen peroxide and dry yeast, vinegar and baking soda,etc.