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

c. heat could easily travel through the molecules in the air and escape/enter the flask. removing the air slows down the heat transfer.  

sry but any answer choices